Downregulation of innate and acquired antitumor immunity by bystander gammadelta and alphabeta T lymphocytes with Th2 or Tr1 cytokine profiles.

It has been thought that natural killer (NK) cells appearing early in tumor lesions play a pivotal role in the innate immunity against tumor cells. Although NK cells serve as the first tumoricidal effector cells, they subsequently promote a shift in effectors from themselves to tumor-specific cytotoxic T lymphocytes (CTLs) that mediate the acquired immunity. The mechanism of this shift has not been fully elucidated, however, NK cell-derived T helper (Th) 1 cytokines such as interferon (IFN)-gamma seem to play a key role. Another NK-lineage, termed natural killer T (NK T) cells, may also participate in the innate period when they acquire the ability to secrete Th1 cytokines. Interleukin-4 (IL-4) and IL-10, belonging to Th2, and transforming growth factor-beta (TGF-beta), belonging to T regulatory (Tr) 1 cytokines, are known to suppress the development of NK, NK T cells, as well as CTLs and to block Th0 cell differentiation to Th1 cells, suggesting that tumor cells can evade the innate and acquired immunity by virtue of cells producing these inhibitory cytokines. In early tumor lesions of murine B16 melanoma, gammadelta T and alphabeta intermediate (int) T cells that co-infiltrate with NK and NK T cells can produce Th2 cytokines and inhibit the innate immunity. In MM2 mammary tumor-bearing mice, gammadelta T cells appearing both lesionally and systemically secrete Tr1-type cytokines and depress the acquired immunity. These Th2- or Tr1-type gammadelta T and alphabeta(int) T cells downregulate the tumoricidal cells by means of both their secreted cytokines and express major histocompatibility complex (MHC) class I molecules.     

Priming of immune responses against transporter associated with antigen processing (TAP)-deficient tumours: tumour direct priming

We previously showed that introduction of transporter associated with antigen processing (TAP) 1 into TAP-negative CMT.64, a major histocompatibility complex class I (MHC-I) down-regulated mouse lung carcinoma cell line, enhanced T-cell immunity against TAP-deficient tumour cells. Here, we have addressed two questions: (1) whether such immunity can be further augmented by co-expression of TAP1 with B7.1 or H-2K^b genes, and (2) which T-cell priming mechanism (tumour direct priming or dendritic cell cross-priming) plays the major role in inducing an immune response against TAP-deficient tumours. We introduced the B7.1 or H-2K^b gene into TAP1-expressing CMT.64 cells and determined which gene co-expressed with TAP1 was able to provide greater protective immunity against TAP-deficient tumour cells. Our results show that immunization of mice with B7.1 and TAP1 co-expressing but not H-2K^b and TAP1 co-expressing CMT.64 cells dramatically augments T-cell-mediated immunity, as shown by an increase in survival of mice inoculated with live CMT.64 cells. In addition, our results suggest that induction of T-cell-mediated immunity against TAP-deficient tumour cells could be mainly through tumour direct priming rather than dendritic cell cross-priming as they show that T cells generated by tumour cell-lysate-loaded dendritic cells recognized TAP-deficient tumour cells much less than TAP-proficient tumour cells. These data suggest that direct priming by TAP1 and B7.1 co-expressing tumour cells is potentially a major mechanism to facilitate immune responses against TAP-deficient tumour cells.     

Inhibition of casein kinase 2 enhances the death ligand- and natural kiler cell-induced hepatocellular carcinoma cell death

Recent studies have shown that the inhibition of casein kinase 2 (CK2) sensitizes many cancer cells to Fas ligand- and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. However, it has not been demonstrated directly whether CK2 inhibition can also enhance the cytotoxicity of natural killer (NK) cells, which actually use the death ligands to kill cancer cells in vivo. To address whether NK cell-mediated cancer cell death is affected by the inhibition of CK2, we first checked whether the death ligand-induced apoptosis of hepatocellular carcinoma cells (HCCs) and HeLa were affected by CK2 inhibition. We then investigated the effect of CK2 inhibition on NK cytotoxicity against HCCs and HeLa cells and its mechanistic features. Inhibition of CK2 by emodin increased the apoptotic cell death of HepG2, Hep3B and HeLa when the cancer cell lines were treated with a soluble form of recombinant TRAIL or an agonistic antibody of Fas. This phenomenon appeared to be correlated with the expression level of death receptors on the cancer cell surface. More interestingly, the inhibition of CK2 also greatly increased the NK cell-mediated cancer cell killing. The NK cytotoxicity against the cancer cells increased about twofold when the target cells were pretreated with a specific CK2 inhibitor, emodin or 4,5,6,7-tetrabromobenzotriazole. Furthermore, the increase of the NK cytotoxicity against cancer cells by CK2 inhibition was granule-independent and mediated possibly by the death ligands on the NK cell surface. This suggests that CK2 inhibitors could be used to enhance the cytotoxicity of NK cells and consequently increase host tumour immunity.     

Expression of recombinant enterotoxigenic Escherichia coli colonization factor antigen I by Salmonella typhimurium elicits a biphasic T helper cell response

Protective immunity to enterotoxigenic Escherichia coli (ETEC) is antibody (Ab) dependent; however, oral immunization with purified ETEC fimbriae fails to elicit protective immunity as a consequence of antigenic alteration by the gastrointestinal (GI) tract. Unless unaltered ETEC fimbriae can reach the inductive lymphoid tissues of the GI tract, immunity to ETEC cannot be induced. To produce immunity, live vectors, such as Salmonella typhimurium, can effectively target passenger antigens to the inductive lymphoid tissues of the GI tract. By convention, oral immunizations with Salmonella vectors induce CD4(+) T helper (Th) cell responses by gamma interferon (IFN-gamma)-dominated pathways both to the vector and passenger antigen, resulting in serum immunoglobulin G2a (IgG2a) and modest mucosal IgA Ab responses. In the present study, mice orally immunized with a Salmonella vector engineered to stably express ETEC colonization factor antigen I (CFA/I) showed initially elevated serum IgG1 and mucosal IgA anti-CFA/I Ab responses. As expected, mice orally immunized with an E. coli-CFA/I construct elicited poor anti-CFA/I Ab responses. In fact, the addition of cholera toxin during oral E. coli-CFA/I immunization failed to greatly enhance mucosal IgA Ab responses. Seven days after immunization with the Salmonella-CFA/I construct, cytokine-specific ELISPOT showed induction of predominant Th2-type responses in both mucosal and systemic immune compartments supporting the early IgG1 and IgA anti-CFA/I Abs. By 4 weeks, the Th cell response became Th1 cell dominant from the earlier Th2-type responses, as evidenced by increased mucosal and systemic IFN-gamma-producing T cells and a concomitant elevation of serum IgG2a Ab responses. This biphasic response offers an alternative strategy for directing Salmonella vector-induced host immunity along a Th2 cell-dependent pathway, allowing for early promotion of mucosal and systemic Abs.     

Antigen-specific memory T cell responses after vaccination with an oral killed cholera vaccine in bangladeshi children and comparison to responses in patients with naturally acquired cholera

Young children, older children, and adults develop comparable levels and durations of immunity following cholera. In comparison, young children receiving oral killed cholera vaccines (OCV) develop a lower level and shorter duration of protection than those of older children and adults. The reasons for this are unclear. We investigated OCV-induced memory T cell responses in younger and older children and compared responses to those in children with cholera. We found that patients with cholera developed significant levels of toxin-specific effector memory T cells (T(EM)) with follicular helper and gut-homing characteristics. Older children (6 to 14 years of age) receiving two doses of OCV containing recombinant cholera toxin B subunit (rCTB) had more modest T(EM) responses with follicular helper and gut-homing characteristics, but younger vaccinees (24 to 71 months of age) did not develop T(EM) responses. The T(EM) response correlated positively with subsequent IgG memory B cell responses specific to rCTB in older vaccinees. Cytokine analyses indicated that cholera patients developed significant Th1, Th17, and Th2 responses, while older children receiving vaccine developed more modest increases in Th1 and Th17 cells. Younger vaccinees had no increase in Th1 cells, a decrease in Th17 cells, and an increase in regulatory T (Treg) cells. Our findings suggest that T cell memory responses are markedly diminished in children receiving OCV, especially young children, compared to responses following naturally acquired cholera, and that these differences affect subsequent development of memory B cell responses. These findings may explain the lower efficacy and shorter duration of protection afforded by OCV in young children.     

Anti-Gal IgG potentiates natural killer cell migration across porcine endothelium via endothelial cell activation and increased natural killer cell motility triggered by CD16 cross-linking

Xenoreactive antibodies (Ab) are important for the development of acute vascular rejection (AVR) of xenografts characterized by monocytes, natural killer (NK) cells and neutrophils infiltrating the graft. The mechanisms by which anti-galactose alpha 1,3galactose (alpha-Gal) IgG influence NK cell migration across porcine aortic endothelium (PAEC) were investigated. NK cell migration across PAEC increased in the presence of anti-alpha-Gal IgG. Anti-alpha-Gal IgG exposure activated PAEC as shown by an increased expression of CD62E and CD106. NK cells adhered, spread and showed motile forms on plastic surfaces coated with human IgG, IgG Fc and on mAb against CD16, but not on mouse IgG or BSA, suggesting that CD16 cross-linking can mediate increased adhesiveness. Increased NK cell motility was observed on Boyden filters coated with human IgG, IgG Fc, and mAb against CD16 and the alpha 4, alpha 5, alpha L, beta 1 and beta 2 integrin chains. No motile response was seen on mouse IgGor CD7, CD56 and alpha 6 integrin mAb. NK cell migration on human IgG and anti-CD16 Ab was blocked by anti-CD16 or anti-beta 2, but not anti-beta 1 Ab, implying that the motile response triggered by CD16 cross-linking is mediated via beta 2 integrins. Preformed or induced anti-alpha-Gal IgG may therefore contribute to AVR by stimulating innate immune cell infiltration of the graft.     

Augmented induction of CD8+ cytotoxic T-cell response and antitumour resistance by T helper type 1-inducing peptide

The effector CD8(+) T cells recognize major histocompatibility complex (MHC) class I binding altered self-peptides expressed in tumour cells. Although the requirement for CD4(+) T helper type 1 (Th1) cells in regulating CD8(+) T cells has been documented, their target epitopes and functional impact in antitumour responses remain unclear. We examined whether a potent immunogenic peptide of Mycobacterium tuberculosis eliciting Th1 immunity contributes to the generation of CD8(+) T cells and to protective antitumour immune responses to unrelated tumour-specific antigens. Peptide-25, a major Th epitope of Ag85B from M. tuberculosis preferentially induced CD4(+) Th1 cells in C57BL/6 mice and had an augmenting effect on Th1 generation for coimmunized unrelated antigenic peptides. Coimmunization of mice with Peptide-25 and ovalbumin (OVA) or Peptide-25 and B16 melanoma peptide [tyrosinase-related protein-2 (TRP-2)] for MHC class I led to a profound increase in CD8(+) T cells specific for OVA and TRP-2 peptides, respectively. This heightened response depended on Peptide-25-specific CD4(+) T cells and interferon-gamma-producing T cells. In tumour protection assays, immunization with Peptide-25 and OVA resulted in the enhancement of CD8(+) cytotoxic cell generation specific for OVA and the growth inhibition of EL-4 thymoma expressing OVA peptide leading to the tumour rejection. These phenomena were not achieved by immunization with OVA alone. Peptide-25-reactive Th1 cells counteractivated dendritic cells in the presence of Peptide-25 leading them to activate and present OVA peptide to CD8(+) cytotoxic T cells.     

Targeted oral delivery of BmpB vaccine using porous PLGA microparticles coated with M cell homing peptide-coupled chitosan

M cells, the key players of the mucosal immunity induction, are one of the intestinal barriers for the efficient delivery of vaccines to mucosal immune tissues. To overcome the barrier, we have developed an efficient oral vaccine carrier that constitutes poly (lactic-co-glycolic acid) (PLGA) microparticle coated with M cell targeting peptide. In this study, a membrane protein B of Brachyspira hyodysenteriae (BmpB) as a model vaccine against swine dysentery was loaded into porous PLGA microparticles (MPs). The PLGA MPs were further coated with the water-soluble chitosan (WSC) conjugated with M cell homing peptide (CKS9) to prepare BmpB-CKS9-WSC-PLGA MPs. Oral immunization of BmpB vaccine with CKS9-WSC-PLGA MPs in mice showed elevated secretory IgA responses in the mucosal tissues and systemic IgG antibody responses, providing a complete immune response. Specifically, the immunization with these MPs demonstrated to induce both Th1- and Th2-type responses based on elevated IgG1 and IgG2a titers. The elevated immune responses were attributed to the enhanced M cell targeting and transcytosis ability of CKS9-WSC-PLGA MPs to Peyer's patch regions. The high binding affinity of CKS9-WSC-PLGA MPs with the M cells to enter into the Peyer's patch regions of mouse small intestine was investigated by closed ileal loop assay and it was further confirmed by confocal laser scanning microscopy. These results suggest that the M cell targeting approach used in this study is a promising tool for targeted oral vaccine delivery.     

No difference in natural killer or natural killer T-cell population, but aberrant T-helper cell population in the endometrium of women with repeated miscarriage

BACKGROUND: The aim of this study was to assess the natural killer (NK) cell and natural killer T (NKT) cell populations and cytokine expression of T-helper (Th) cells in the endometrium of women who suffered from unexplained repeated miscarriage (RM). METHODS: The percentages of NK cells, NKT cells and CD4(+) cells expressing intracellular interferon (IFN)-gamma, interleukin (IL)-4 and tumour necrosis factor (TNF)-alpha were measured by flow cytometry in the endometrium of 20 RM women and 17 fertile control women in the mid-luteal phase of the menstrual cycle. RESULTS: No significant differences in CD56(+) NK cell or CD3(+)CD4(-)CD8(-)Valpha24(+)Vbeta11(+) NKT cell percentages were found between RM and control women. However, in RM women compared with control women, the percentages of CD3(+) cells (mean 40.3 versus 56.5%), CD4(+)IFN-gamma(+) cells (28.4 versus 39.5%) and CD4(+)TNF-alpha(+) cells (32.9 versus 45.8%) were significantly lower. The Th1/Th2 cell balance in RM women did not differ from that of controls. CONCLUSIONS: Immunodystrophism detected as diminution of the Th cell population rather than Th1 predominance, NK cell or NKT cell accentuation in the endometrium might underlie the pathophysiology of unexplained RM. This finding provokes an additional controversy on the Th1/Th2 balance concerning RM aetiology.     

A vaccine conjugate of 'ISCAR' immunocarrier and peptide epitopes of the E7 cervical cancer-associated protein of human papillomavirus type 16 elicits specific Th1- and Th2-type responses in immunized mice in the absence of oil-based adjuvants.

TraT protein, known as ISCAR (= Immunostimulatory Carrier), is one of a family of integral membrane proteins (Imps) of Escherichia coli representing powerful carrier molecules which when injected into experimental animals generate substantial antibody and T proliferative responses to molecules conjugated to it. We extend these findings to show that ISCAR functions to stimulate Th1- and Th2-type responses, including specific cytotoxic T cells and tumour protection. We report here that by conjugating to ISCAR a 19mer peptide containing linear B epitopes, a T helper (Th) epitope, and a H-2b-restricted T cytotoxic (CTL) epitope of E7 protein of human papillomavirus type 16 (HPV16), and immunizing C57B1/6 (H-2b) mice, we elicited (i) specific IgG2a and IgG1 antibodies; (ii) IL-2 and IL-4 production by specifically recalled lymph node cells in vitro; (iii) cytotoxic T lymphocytes which specifically killed both E7 peptide-pulsed, and whole E7 gene-transfected tumour target cells; and (iv) in vivo protection against an E7 gene-transfected tumour cell inoculum. These findings have implications for the design of vaccines to stimulate immune responses to endogenously processed target antigens (e.g. tumour-associated antigens) without the unwanted side effects of oil-based adjuvants. In addition they support the case for a E7-targeted therapeutic vaccine for HPV-associated human cervical cancer.     

Defective NK cell activity following thermal injury.

Peripheral blood mononuclear lymphocytes (PBL) from thermal injury patients were examined for their ability to mediate natural killer (NK) cell activity against K562 tumour cells and against herpes simplex virus type 1 (HSV-1) infected Raji tumour cells. Using fluorescein isothiocyanate-conjugated monoclonal antibodies, the number of T3, T4, T8, Leu11, and Leu7 positive cells in PBL obtained from patients and normal controls was determined. Thermal injury patients had decreased levels of T3+ cells and a T4:T8 ratio which was significantly lower than that found in normal control individuals. Although patients had normal percentages of Leu7+ and Leu11+ cells, they had depressed NK cell activity against both K562 tumour cells and HSV-1 infected Raji cells. NK cell activity against K562 tumour cells was severely depressed during the first 20 days after injury. This defective NK cell activity did not appear to be due to a defect in PBL binding to the K562 tumour cells. In patients, the level of NK cell activity against HSV-1 infected cells did not correlate with the level of NK cell activity against K562 tumour cells. This finding further supports previous reports showing that NK cells which kill K562 tumour cells are different from the NK cell population which kills HSV-1 infected cells. Pretreatment of PBL obtained from patients with IL-2 or IFN-alpha, in some cases greatly enhanced NK cell killing of K562 tumour cells. However, IL-2 or IFN-alpha did not enhance NK cell activity in patients who had severely depressed levels of NK cell activity. Interestingly, in some patients, differential responsiveness to IL-2 and IFN-alpha was observed. In some patients, NK cell activity was enhanced by IL-2 but not by IFN-alpha. These results, while only suggestive, may indicate that different populations of NK cells respond preferentially to IL-2 and that IFN-alpha and/or IL-2 enhance NK cell activity in PBL obtained from some, but not all, thermal injury patients. Finally, this study clearly shows that thermal injury patients have defective NK cell activity not only against K562 tumour cells but also against virus-infected cells.     

Early-appearing tumour-infiltrating natural killer cells play a crucial role in the generation of anti-tumour T lymphocytes.

Natural killer (NK) cells that infiltrated into the primary tumour site at an early stage of tumour development, were examined for their participation in the generation of anti-tumour cytotoxic T lymphocytes (CTL). NK cells, which were detected by anti-NK1.1 monoclonal antibody (mAb), increased in the peritoneal exudate cells (PEC) on days 3 and 7 after an intraperitoneal (i.p.) inoculation of syngeneic B16 melanoma cells. These tumour-infiltrating NK cells showed a high level of cytotoxic activity against NK-sensitive YAC-1 cells and an increased expression of interferon-gamma (IFN-gamma) mRNA and interleukin-2 (IL-2) mRNA. The in vivo depletion of NK cells with anti-NK1.1 mAb, prior to i.p. inoculation of B16 melanoma cells, resulted in an increased number of tumour cells in the PEC compared to NK cell non-depleted mice. Interestingly, the differences in tumour cell number between both groups were more prominent on days 7 and 14 than on day 3, which strongly suggested that early-infiltrating NK cells have a large influence on the subsequent anti-tumour response. The in vivo depletion of NK cells prior to immunization with melanoma cells abrogated the capacity of the spleen cells to generate CD8+ tumour-specific CTL after in vitro restimulation. This inability of generating anti-tumour CTL was partially restored by additional i.p. injections of recombinant IL-2 and/or IFN-gamma simultaneously with the immunization of melanoma cells. The in vitro depletion of NK cells prior to the in vitro restimulation with melanoma cells partially impaired the anti-tumour CTL generation from the spleen cells of the immunized mice. Lastly, the in vivo depletion of NK cells prior to immunization with melanoma cells abolished the protective immunity against melanoma cells at the rechallenge. Overall, these results indicate that early-appearing tumour-infiltrating NK cells not only participate in the anti-tumour early defence by themselves, but also play a crucial role in the generation of anti-tumour CTL.     

Presentation of high antigen‐dose by splenic B220lo B cells fosters a feedback loop between T helper type 2 memory and antibody isotype switching

Effective humoral immunity ensues when antigen presentation by B cells culminates in productive cooperation with T lymphocytes. This collaboration, however, remains ill‐defined because naive antigen‐specific B cells are rare and difficult to track in vivo. Herein, we used a defined transfer model to examine how B lymphocytes, as antigen‐presenting cells, shape the development of T‐cell memory suitable for generation of relevant antibody responses. Specifically, we examined how B cells presenting different doses of antigen during the initial priming phase shape the development of CD4 T‐cell memory and its influence on humoral immunity. The findings indicate that B cells presenting low dose of antigen favour the development of T helper type 1 (Th1) type memory, while those presenting a high antigen dose yielded better Th2 memory cells. The memory Th2 cells supported the production of antibodies by effector B cells and promoted isotype switching to IgG1. Moreover, among the B‐cell subsets tested for induction of Th2 memory, the splenic but not peritoneal B220^lo cells were most effective in sustaining Th2 memory development as well as immunoglobulin isotype switching, and this function involved a tight control by programmed death 1–programmed death ligand 2 interactions.     

CD4 and IL-2 mediated NK cell responses after COVID-19 infection and mRNA vaccination in adults

A detailed understanding of protective immunity against SARS-CoV-2 is incredibly important in fighting the pandemic. Central to protective immunity is the ability of the immune system to recall previous exposures. Although antibody and T cell immunity have gained considerable attention, the contribution of the NK cell compartment to immune recall and protection from SARS-CoV-2 has not been explored. In this study, we investigate the NK cell responses to stimulation with SARS-CoV-2 in previously exposed and non-exposed individuals. We show that NK cells demonstrate an enhanced CD4+ T cell dependent response when re-exposed to SARS-CoV-2 antigen. The enhanced response is dependent on T cells and correlates with the number of SARS-CoV-2 specific CD4 T cells. We find that IL-2 is a critical mediator of NK cell function. These findings suggest that NK cells contribute to the protective responses against SARS-CoV-2 through a cooperation with antigen-specific CD4 T cells and have significant implications on our understanding of protective immunity in SARS-CoV-2.     

Unifying concepts of MHC-dependent natural killer cell education

Natural killer (NK) cells, like B and T lymphocytes, are potent effector cells that are crucial for immunity to tumors and infections. These effector responses must be controlled to avoid inadvertent attack against normal self. Yet, the mechanisms that guide NK cell tolerance differ from those guiding T and B cell tolerance. Here, we discuss how NK cells are licensed by self-MHC class I molecules through their inhibitory receptors which results in NK cell functional competence to be triggered through their activation receptors. We discuss recent data with respect to issues related to licensing, thereby providing a framework for unifying concepts on NK cell education.     

CD19-deficient mice exhibit poor responsiveness to oral immunization despite evidence of unaltered total IgA levels, germinal centers and IgA-isotype switching in Peyer's patches

CD19 exhibits a critical role as a response regulator in B cells, influencing activation, differentiation and survival. Accordingly, CD19-deficient mice largely lack B-1 cells, and their conventional B-2 cells are poor responders to thymus-dependent antigen. Since both B-1 and B-2 cells may contribute to the total intestinal IgA production, we investigated whether lack of CD19 negatively affected mucosal immunity. We found that CD19(-/-) mice have near normal total IgA levels in serum and gut mucosa and, contrary to systemic lymphoid tissues, Peyer's patches (PP) had germinal centers to which also IgA+ B cells localized. However, the mice demonstrated severely impaired responses to oral immunization with keyhole limpet hemocyanin plus cholera toxin adjuvant. Mucosal responses to oral immunization were significantly more impaired than systemic responses. Despite normal specific IL-4 production, a selective defect in Th2-regulated B cell isotypes was observed, with poor or no mucosal IgA, low serum IgG1 and no IgE, but intact serum IgA and IgG2a production. Ex vivo experiments revealed strongly inhibited CD40-stimulated proliferation and IgA differentiation in CD19-deficient PP B cells. Taken together, an impaired CD40 responsiveness selectively affected Th2, but not Th1, coordinated B cell responses. The CD19(-/-) mice provide compelling evidence for the differential regulation of serum and mucosal IgA immunity.     

1,25‐Dihydroxy‐vitamin D3 regulates NK‐cell cytotoxicity,cytokine secretion,and degranulation in women with recurrent pregnancy losses

Vitamin D has a pivotal role in regulating immune responses by promoting Th2 immune responses and suppressing Th1 responses. Propensities to a Th1 immune response and increased NK‐cell levels and cytotoxicity have been reported in women with recurrent pregnancy losses (RPL). In women with RPL, vitamin D deficiency is prevalent; however, the effect of vitamin D on NK cells is largely unknown. In this study, we demonstrated that CD69⁺ activating receptor expression on NK cells was significantly decreased by incubation with 1,25(OH)₂D₃ in a dose‐dependent manner, while CD158a and CD158b inhibitory receptor expression was upregulated. The degranulation marker CD107a was significantly downregulated on NK cells following incubation with 1,25(OH)₂D₃. NK‐cell conjugation with K562 target cells was not affected by 1,25(OH)₂D₃; however, depolarization of perforin granules in conjugated NK cells was significantly increased. TLR4 expression on NK cells was significantly decreased and TNF‐α and IFN‐γ production was significantly reduced by 1,25(OH)₂D₃ through interference with NF‐κB. Our results suggest 1,25(OH)₂D₃ has immune regulatory effects on NK cell cytotoxicity, cytokine secretion and degranulation process as well as TLR4 expression. Potential therapeutic application of 1,25(OH)₂D₃ for dysregulated NK‐cell immunity should be explored in the future.     

Optimizing dendritic cell vaccine for immunotherapy in multiple myeloma: tumour lysates are more potent tumour antigens than idiotype protein to promote anti-tumour immunity

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the mediators of T cell immunity. Many investigators have explored the potential of using DCs as a vaccine for tumour-derived antigens in immunotherapy of B cell malignancies, and the results have been disappointing. To search for better tumour antigens to improve the efficacy of DC-based immunotherapy in myeloma, we evaluated and compared the efficacy of the vaccination of DCs pulsed with idiotype (Id) or tumour lysate in the 5TGM1 myeloma mouse model. Our results showed that Id- or tumour lysate-pulsed DC vaccines protected mice efficiently against developing myeloma, retarded tumour growth, induced tumour regression against established tumour and protected surviving mice from tumour rechallenge. The therapeutic responses were associated with an induction of strong humoral immune responses, including anti-Id or anti-lysate antibodies, and cellular immune responses including myeloma-specific CD8⁺ cytotoxic T lymphocytes, CD4⁺ type 1 T helper cells and memory T cells in mice receiving Id- or tumour lysate-pulsed DC vaccines. In addition, our studies showed that tumour lysate-pulsed DCs were more potent vaccines than the Id-pulsed DC vaccines to promote anti-tumour immunity in the model. This information will be important for improving the strategies of DC-based immunotherapy for patients with myeloma and other B cell tumours.     

Current developments in viral DNA vaccines: shall they solve the unsolved?

This review describes the mechanisms of immune response following DNA vaccination. The efficacy of DNA vaccines in animal models is highlighted, especially in viral diseases against which no widely accepted vaccination is currently available. Emphasis is given to possible therapeutic vaccination in chronic infections due to persisting virus genomes, such as recurrent herpes (HSV-1 and HSV-2), pre-AIDS (HIV-1) and/or chronic hepatitis B (HBV). In these, the problem of introducing foreign viral DNA may not be of crucial importance, since the immunised subject is already a viral DNA (or provirus) carrier. The DNA-based immunisation strategies may overcome several problems of classical viral vaccines. Novel DNA vaccines could induce immunity against multiple viral epitopes including the conservative type common ones, which do not undergo antigenic drifts. Within the immunised host, they mimic the effect of live attenuated viral vaccines when continuously expressing the polypeptide in question. For this reason they directly stimulate the antigen-presenting cells, especially dendritic cells. The antigen encoded by plasmid elicits T helper cell activity (Th1 and Th2 type responses), primes the cytotoxic T cell memory and may induce a satisfactory humoral response. The efficacy of DNA vaccines can be improved by adding plasmids encoding immunomodulatory cytokines and/or their co-receptors.