Importance of murine Vdelta1gammadelta T cells expressing interferon-gamma and interleukin-17A in innate protection against Listeria monocytogenes infection

Murine gammadelta T cells participate in the innate immune response against infection by an intracellular pathogen Listeria monocytogenes. Vdelta1+gammadelta T cells coexpressing Vgamma6 are a major gammadelta T-cell subpopulation induced at an early stage of L. monocytogenes infection in the livers of infected mice. To investigate the protective role of the Vgamma6/Vdelta1+gammadelta T cells against L. monocytogenes infection, Vdelta1 gene-deficient (Vdelta1-/-) mice were analysed because these mice selectively lacked a Vgamma6/Vdelta1+gammadelta T-cell subpopulation in the L. monocytogenes-infected liver. The Vdelta1-/- mice showed increased bacterial burden in the liver and spleen, and decreased survival rate at an early stage of L. monocytogenes infection when compared to wild-type mice. Histological examination showed abscess-like lesions and unorganized distribution of macrophages in the liver of the Vdelta1-/- mice but not in the wild-type mice after L. monocytogenes infection. The Vgamma6/Vdelta1+gammadelta T cells produced interferon-gamma and interleukin-17A. All the results suggest that murine Vgamma6/Vdelta1+gammadelta T cells control the innate protective response against L. monocytogenes infection through production of the proinflammatory cytokines interferon-gamma and interleukin-17A in the infected liver.     

The suppression of delayed-type hypersensitivity by CD8+ regulatory T cells requires interferon-gamma

CD8(+) regulatory (suppressor) T cells are induced by complex cellular pathways in the spleens of mice that have received an injection of antigen into the anterior chamber (AC) of an eye, an immune-privileged site. Although these CD8(+) regulatory T cells perform an antigen-specific regulatory function for an immune response to self and non-self antigens, the mechanisms of the activation or function of these regulatory cells are not clear. Here, we describe a novel mechanism for the activation of splenic CD8(+) regulatory T cells induced by injection of antigen into the AC. Immunization of mice with trinitrophenyl and bovine serum albumin (TNP-BSA) amplified AC-induced splenic CD8(+) regulatory T cells that suppressed the initiation of contact sensitivity when transferred to immunized, challenged mice. These CD8(+) regulatory T cells were produced independently of perforin, indicating that they are not canonical cytotoxic T cells. Fas ligand (FasL)-deficient CD8(+) regulatory T-cell function was rescued by inclusion of exogenous interferon-gamma (IFN-gamma), demonstrating that the expression of FasL by CD8(+) regulatory T cells was dispensable, but IFN-gamma was not. Ultimately, we demonstrated that the generation of these CD8(+) regulatory T cells occurred independently of IFN-gamma, but their suppressor function required IFN-gamma receptor stimulation.     

TCR-beta chains derived from peripheral gammadelta T cells can take part in alphabeta T-cell development

Between 10 and 20% of the peripheral gammadelta T cells express cytoplasmic TCR-beta proteins, but whether such TCR-beta chains can partake in alphabeta T-cell development has never been systematically investigated. Therefore, we reconstituted the T-cell compartment of CD3epsilon-deficient mice with Pax5-TCR-beta deficient proB cells expressing, via a retroviral vector, TCR-beta chains from either peripheral gammadelta or alphabeta T cells. Recipient thymi reconstituted with proB cells containing empty vector were small (<15x10(6) cells), contained few gammadelta T but no alphabeta T cells. In contrast, thymi from mice receiving proB cells containing gammadelta or alphabeta T-cell-derived TCR-beta chains contained 80-130x10(6) cells, and showed a normal CD4, CD8 and alphabeta TCR expression pattern. However, regardless of the source of TCR-beta chain, reconstituted mice rapidly showed signs of autoimmunity dying 5-15 wk following reconstitution. Autoimmune disease induction could be prevented by co-transfer of Treg cells thereby allowing the functionality of the generated T cells to be assessed. Results obtained show that TCR-beta chains from gammadelta T cells can efficiently take part in alphabeta T-cell development. The implications of these findings for gammadelta T-cell development will be discussed.     

Reciprocal stimulation of gammadelta T cells and dendritic cells during the anti-mycobacterial immune response

Gammadelta T cells and dendritic cells (DC) are two distinct cell types of innate immunity that participate in early phases of immune response against Mycobacterium tuberculosis infection. Here we show that a close functional relationship exists between these cell populations. Using an in vitro coculture system, Vgamma1 T cells from Tcrb(-/- )mice were found to be activated by DC infected in vitro with BCG, as indicated by the elevated CD69 expression, IFN-gamma secretion and cytotoxic activity. This activation process was due to a non-cognate mechanism since it required neither cell to cell contact nor interaction between the TCR and a specific antigen, but was mediated by DC-derived IL-12. Reciprocally, Vgamma1 T cells provided a key cytokine, IFN-gamma, which increased IL-12 production by BCG-infected DC. Moreover, exposure of BCG-infected DC to Vgamma1 T cells conditioned the former to prime a significantly stronger anti-mycobacterial CD8 T cell response. Consequently, stimulation of gammadelta T cells and their non-cognate interaction with DC could be applied as an immune adjuvant strategy to optimize vaccine-induced CD8 T cell immunity.     

Yes T cells, but three different T cells (alphabeta, gammadelta and NK T cells), and also B-1 cells mediate contact sensitivity

Transfer of contact sensitivity (CS) responses by immune lymphoid cells was the first finding that distinguished cellular from humoral immunity. CS has remained the most studied T cell reaction in vivo, and is the prototype for a variety of delayed-type hypersensitivity (DTH) responses. DTH in essence is the recruitment of effector alphabeta-T cells out of vessels into peripheral tissues. The T cells then are activated by antigen presenting cells to produce pro-inflammatory cytokines. It has been assumed that the alphabeta-T cells alone are responsible, but recent studies show that three other lymphocyte subsets are involved: CS-inducing NK T cells, CS-initiating B-1 cells, and CS-assisting gammadelta-T cells. Therefore, the effector alphabeta-T cells are essential, but cannot be recruited into the tissues without the local action of IgM antibodies produced by B-1 cells rapidly (1 day) post-immunization. The IgM complexes with the challenge antigen to locally activate complement to lead to vascular activation required for T cell recruitment. This process occurs early (1-2 hours) in the elicitation phase, and is called CS-initiation. The essential CS-inducing NK T cells activate the B-1 cells by producing IL-4 rapidly (1 hour) after immunization, and gammadelta-T cells assist the local inflammatory function of the recruited CS-effector alphabeta-T cells. Thus, four lymphocyte subsets are required for elicitation of responses: CS-inducing NK T cells, CS-initiating B-1 cells, CS-assisting gammadelta-T cells, and finally the CS-effector alphabeta-T cells. Three of these four cell types are present in the immune lymphoid cell population that adoptively transfers CS: B-1 cells, gammadelta-T cells, and the alphabeta-T cells.     

Interleukin (IL)-4 promotes T helper type 2-biased natural killer T (NKT) cell expansion, which is regulated by NKT cell-derived interferon-gamma and IL-4

CD1d-restricted natural killer T (NKT) cells can rapidly produce T helper type 1 (Th1) and Th2 cytokines and also play regulatory or pathological roles in immune responses. NKT cells are able to expand when cultured with alpha-galactosylceramide (alpha-GalCer) and interleukin (IL)-2 in a CD1d-restricted manner. However, the expansion ratio of human NKT cells is variable from sample to sample. In this study, we sought to determine what factor or factors are responsible for efficient in vitro expansion of NKT cells from various inbred mouse strains. Although the proportion of NKT cells in the spleen was nearly identical in each mouse strain, the growth rates of NKT cells cultured in vitro with alpha-GalCer and IL-2 were highly variable. NKT cells from the B6C3F1 and BDF1 mouse strains expanded more than 20-fold after 4 days in culture. In contrast, NKT cells from the strain C3H/HeN did not proliferate at all. We found that cell expansion efficiency correlated with the level of IL-4 detectable in the supernatant after culture. Furthermore, we found that exogenous IL-4 augmented NKT cell proliferation early in the culture period, whereas interferon (IFN)-gamma tended to inhibit NKT cell proliferation. Thus, the ratio of production of IL-4 and IFN-gamma was important for NKT cell expansion but the absolute levels of these cytokines did not affect expansion. This finding suggests that effective expansion of NKT cells requires Th2-biased culture conditions.     

Reduction of forkhead box P3 levels in CD4+CD25high T cells in patients with new-onset systemic lupus erythematosus

The aim of this study was to quantify and evaluate the forkhead box P3 (FoxP3) expression regulatory T cells in new-onset systemic lupus erythematosus (SLE) patients before and after treatment. Forty-four newly diagnosed and untreated SLE patients, including 24 with active disease (SLEDAI > or = 10) and 20 with inactive disease (SLEDAI < 5), were enrolled in this study. Twenty-one age- and sex-matched healthy volunteers were also included as controls. Peripheral blood samples were collected and mononuclear cells isolated. The expression of CD25 and FoxP3 in CD4(+) T cells were analysed with flow cytometry. CD4(+)CD25(+) (3.95-13.04%) and CD4(+)CD25(high) (0.04-1.34%) T cells in peripheral blood in untreated patients with new-onset active lupus were significantly lower than that in the patients with inactive lupus (7.27-24.48%, P < 0.05 and 0.14-3.07% P < 0.01 respectively) and that in healthy controls (5.84-14.84%, P < 0.05). Interestingly, the decrease in CD4(+)CD25(high) T cells was restored significantly in patients with active lupus after corticosteroid treatment. There was, however, a significantly higher percentage of CD4(+)FoxP3(+) T cells in patients with active (5.30-23.00%) and inactive (7.46-17.38%) new-onset lupus patients compared with healthy control subjects (2.51-12.94%) (P < 0.01). Intriguingly, CD25 expression in CD4(+)FoxP3(+) T cells in patients with active lupus (25.24-62.47%) was significantly lower than that in those patients with inactive lupus (30.35-75.25%, P < 0.05) and healthy controls (54.83-86.38%, P < 0.01). Most strikingly, the levels of FoxP3 expression determined by mean fluorescence intensity in CD4(+)CD25(high) cells in patients with active SLE were significantly down-regulated compared with healthy subjects (130 +/- 22 versus 162 +/- 21, P = 0.012). CD4(+)CD25(high) T cells are low in new-onset patients with active SLE and restored after treatment. Despite that the percentage of CD4(+)FoxP3(+) T cells appear high, the levels of FoxP3 expression in CD4(+)CD25(high) T cells are down-regulated in untreated lupus patients. There is a disproportional expression between CD25(high) and FoxP3(+) in new-onset patients with active SLE.     

Density of γ/δ+ T cells in the jejunal epithelium of patients with coeliac disease and dermatitis herpetiformis is increased with age

Increased density of γ/δ T cell receptor (TCR)⁺ intraepithelial lymphocytes is the only characteristic in the jejunum of patients with coeliac disease and dermatitis herpetiformis which is not normalized on a gluten-free diet. We explored the age-dependent changes in intraepithelial γ/δ and α/β TCR⁺ cells from 137 biopsies from patients with coeliac disease and dermatitis herpetiformis and from controls. Biopsy specimens from 100 patients with coeliac disease and dermatitis herpetiformis and from 37 controls were studied with an immunohistochemical method using MoAbs to T cell receptors and peroxidase staining. An increase in the density of intraepithelial γ/δ T cells above the mean +2 s.d. of the density in controls was present in 97 of 100 specimens from patients with coeliac disease and dermatitis herpetiformis. The density of γ/δ⁺ cells of patients with coeliac disease and dermatitis herpetiformis on a normal gluten-containing diet showed a positive correlation with age (r = 0.45, P< 0.0001). In controls, the density of γ/δ⁺ cells remained low throughout the age-range studies, from age 0.6–57 years. In controls, α/β⁺ cells increased with age (r = 0.57, P< 0.001). The increase in density of intraepithelial lymphocytes with age is in agreement with their thymus-independent character and local proliferation.     

CD4+CD29+T cells are blamed for the persistent inflammatory response in ulcerative colitis

Ulcerative colitis (UC) is a chronic gastrointestinal disorder eliciting occurrence of colorectal cancer, the third most common human malignancy. The diagnosis of UC is based on clinical symptoms combined with typical findings on endoscopy, radiology, and ultimately pathology. We investigated the variation trend of CD4⁺CD29⁺T cells together with MPO, VCAM-1 in different periods of rat UC model and UC patients. We also evaluated the relationship between CD4⁺CD29⁺T cells and disease severity. UC model was induced by administering DNCB liquid and acetate solution. We found upregulated expression of CD4⁺CD29⁺T cells in both peripheral blood and colon from rats, and a similar trend for MPO and VCAM-1 in colon (P < 0.05); the expression was especially enhanced in UC rats at two weeks after the model was established (P < 0.01). Such upregulation was also indicated in active and remission UC patients as compared to the healthy and enteritis groups (P < 0.05), with the highest expression level detected in the active UC patients (P < 0.01). Pearson correlation analysis showed a positive correlation of CD4⁺CD29⁺T cells in rat and human peripheral blood with DAI score (r_rat = 0.712, r_human = 0.677, P < 0.01), and MPO in colon (r_rat = 0.514, r_human = 0.682, P < 0.05). These results suggest that CD4⁺CD29⁺T cells may act as major effector cell subsets in persistent inflammatory responses for UC and that infiltration into colon inflammation may be induced by the combination of VCAM-1 and CD29.     

Early coupled up-regulation of interleukin-12 receptor beta-1 in CD8+ central memory and effector T cells for better clinical outcomes in liver transplant recipients

This study aimed to investigate the role of initial priming of interleukin (IL)-12 receptor beta-1 in CD8⁺central memory T cells (initial IL-12RT_CM priming) and CCR7-negative subsets (CNS) in effector cell expansion and clinical outcome after living donor liver transplantation (LDLT). One hundred and six patients who underwent LDLT were classified into the following three groups according to hierarchical clustering of CD8⁺CD45 isoforms before LDLT: I, naive-dominant; II, effector memory-dominant; and III, effector-dominant. The pre-existing CD8⁺effector cells (T_E) and activated immune status increased progressively from group I to group II to group III. Groups I, II and III received tacrolimus (Tac)/glucocorticoid (GC) regimens. Eighteen group III recipients received Tac/mycophenolate mofetil (MMF) and were defined as group IV. Initial IL-12RT_CM priming was slightly, moderately and markedly decreased in droups I, II, and III, respectively. Initial priming of IL-12Rβ1 in CNS was decreased markedly in the three groups with marked decreases of T_E, perforin and interferon (IFN)-γ; all parameters were restored by up-regulation of IL-12Rβ1⁺T_CM through the self-renewal of T_CM. The lag time required until coupled up-regulation of IL-12Rβ1 of T_CM and CNS to above baseline was 12, 20 and 32 days in groups I, II and III, respectively. Inferior clinical outcomes were associated with increasing lag time. In contrast, the initial priming of IL-12Rβ1 in T_CM and CNS remained above baseline in group IV due to MMF-mediated increase of IL-12Rβ1. Early coupled up-regulation of T_CM and CNS leads to efficient T_E differentiation and optimal clinical outcomes.     

T cells developing in fetal thymus of T-cell receptor alpha-chain transgenic mice colonize gammadelta T-cell-specific epithelial niches but lack long-term reconstituting potential

The gammadelta T cells generated during mouse fetal development are absolutely dependent on their invariant T-cell receptors (TCRs) for their function. However, there is little information on whether the epithelial homing properties of fetal T cells might also be developmentally induced by factors unrelated to TCR specificity. We have previously described TCR alpha-chain transgenic (2B4 TCR-alpha TG) mice, in which the transgenic TCR alpha-chain is expressed early, already at embryonic day 14 (E14). These mice have a large population of 'gammadelta T-cell-like' CD4- CD8- (double-negative; DN) alphabeta T cells, some of which develop during E14-E18 contemporarily to intraepithelial lymphocytes (IELs) expressing invariant TCR-gammadelta. Using the 2B4 TCR-alpha TG mouse model we have been able to more precisely study the impact of a variant TCR expression on IEL development and homing. In this study we show that TCR-alpha TG and TCR-alpha TG crossed to TCR-delta-deficient mice (TCR-alpha TG x TCR-delta-/-) carry TG TCR-alpha+ dendritic epidermal T cells (DETCs) and TCR-alpha TG+ IELs in the small intestine. The TG+ DETCs develop and seed the epidermis with similar kinetics as Vgamma5+ DETCs of normal mice, in contrast to the TCR-alphabeta+ DETCs found in TCR-delta-/- mice. However, whereas the intestinal TCR-alpha TG+ IELs persist in old mice (> 20 months), the TCR-alpha TG+ DETCs do not. The data in this study indicate that the timing of TCR expression and thereby development during ontogeny regulates the specific homing potential for fetal T cells but not their subsequent functions and properties.     

Cell-surface bound pertussis toxin induces polyclonal T cell responses with high levels of interferon-gamma in the absence of interleukin-12

Pertussis toxin (PTx), an exotoxin produced by Bordetella pertussis, has long been used as a mucosal adjuvant. We examined the T cell stimulatory properties of PTx in order to dissect its mechanisms of adjuvanticity. PTx or the B-oligomer of PTx (PTxB) failed to activate purified murine CD4+ or CD8+ T cells, as measured by a lack of proliferation or expression of early T cell activation markers. However, these T cells proliferated extensively in response to the toxin in the presence of syngeneic DC, and proliferation was accompanied by a high level of IFN-gamma production in the absence of IL-12. Interestingly, such responses were independent of signals mediated by MHC-TCR interaction. Both PTx and PTxB were found to bind stably to the surface of DC, and increased the adherence of DC to surrounding cells. These data suggest that polyclonal T cell responses mediated by the toxin are likely to be caused by the toxin bound on the surface of APC, either cross-linking cell surface molecules on T cells, or directly stimulating T cells together with the co-stimulatory molecules expressed on APC. B. pertussis may use this toxin as a mechanism to evade a specific immune response.     

Alterations of peripheral CD4+CD25+Foxp3+ T regulatory cells in mice with STZ-induced diabetes

Complications arising from abnormal immune responses are the major causes of mortality and morbidity in diabetic patients. CD4+CD25+T regulatory cells (Tregs) play pivotal roles in controlling immune homeostasis, immunity and tolerance. The effect of hyperglycemia on CD4+CD25+Tregs has not yet been addressed. Here we used streptozotocin (STZ)-induced diabetic mice to study the effects of long-term hyperglycemia on CD4+CD25+Tregs in vivo. Four months after the onset of diabetes, the frequency of CD4+CD25+Foxp3+ T regulatory cells was significantly elevated in the spleen, peripheral blood lymphocytes (PBLs), peripheral lymph nodes (pLNs) and mesenteric LNs (mLNs). CD4+CD25+Tregs obtained from mice with diabetes displayed defective immunosuppressive functions and an activated/memory phenotype. Insulin administration rescued these changes in the CD4+CD25+ Tregs of diabetic mice. The percentage of thymic CD4+CD25+ naturally occurring Tregs (nTregs) and peripheral CD4+Helios+Foxp3+ nTregs were markedly enhanced in diabetic mice, indicating that thymic output contributed to the increased frequency of peripheral CD4+CD25+Tregs in diabetic mice. In an in vitro assay in which Tregs were induced from CD4+CD25- T cells by transforming growth factor (TGF)-β, high glucose enhanced the efficiency of CD4+CD25+Foxp3+ inducible Tregs (iTregs) induction. In addition, CD4+CD25- T cells from diabetic mice were more susceptible to CD4+CD25+Foxp3+ iTreg differentiation than those cells from control mice. These data, together with the enhanced frequency of CD4+Helios-Foxp3+ iTregs in the periphery of mice with diabetes, indicate that enhanced CD4+CD25+Foxp3+ iTreg induction also contributes to a peripheral increase iCD4+CD25+Tregs in diabetic mice. Our data show that hyperglycemia may alter the frequency of CD4+CD25+Foxp3+ Tregs in mice, which may result in late-state immune dysfunction in patients with diabetes.     

Induction of CD56+ T cells after prolonged activation of T cells in vitro: a possible mechanism for CD4+ T-cell depletion in acquired immune deficiency syndrome patients

The pathogenic mechanisms responsible for depletion of CD4(+) T cells in aquired immune deficiency syndrome (AIDS) are not fully understood. Systemic immune activation mediated by persistent infection of human immunodeficiency virus (HIV) seems to be one of the predictors of disease progression. We predicted that certain lymphocytes responsible for CD4(+) T-cell depletion could be induced in patients during prolonged activation of lymphocytes. Therefore, we have established an in vitro long-term culture system for peripheral blood mononuclear cells with PHA-P stimulation and Herpesvirus saimiri infection, and examined what types of cells having strong cytotoxic activity to be emerged under the activated conditions. We observed that percentage of CD56(+) T cells was gradually increased in cultures from 30 days after stimulation and exhibited a cytotoxic activity against both autologous and allogeneic targets. Interestingly, HIV-1 infection enhanced the susceptibility of CD4(+) T cells to their cytotoxic effectors, and CD4(+) T cells from HIV-1-infected individuals showed decreased survival rate in the presence of autologous CD56(+) T cells. These findings raised the possibility that induction of autoreactive CD56(+) T cells in consequence of immune activation might be contributed to the depletion of CD4(+) T cells in HIV-1-infected patients.     

Interleukin-4 suppresses the cytotoxic potential of in vitro generated,adaptive regulatory CD4+ T cells by down-regulation of granzyme B

Regulatory CD4⁺ T cells (Tregs) control immune responses using secretion of anti-inflammatory cytokines and/or cytotoxic mechanisms and play a central role in the outcomes of several immune pathologies. Previous studies suggest an impaired function of Tregs in allergy, especially during allergen seasons, but the underlying mechanism is not known. Therefore, we analysed the impact of the T helper type 2 cytokine interleukin (IL)-4 on in vitro generated adaptive Tregs (aTregs), which have been reported to use the granzyme B (GrB)/perforin pathway to kill autologous immune cells. aTregs were generated by co-ligation of CD3 and CD46 on CD4⁺ T lymphocytes and granzyme expression was analysed using flow cytometry. To quantify GrB and perforin expression as well as IL-10 secretion in response to IL-4, specific enzyme-linked immunosorbent assays were performed in cell lysates and/or culture supernatants. Using a flow cytometry-based cytotoxicity assay the impact of IL-4 on the cytotoxic potential of aTregs was investigated. While IL-4 did not affect IL-10 secretion and perforin expression in aTregs, a significant suppression of GrB synthesis was detected in the presence of IL-4. In addition, IL-4-mediated suppression of GrB led to impaired cytotoxicity of aTregs against K562 target cells. In conclusion, our data suggest that IL-4 might play a role in impaired aTreg function in allergy.     

Involvement of Foxp3-expressing CD4+ CD25+ regulatory T cells in the development of tolerance induced by transforming growth factor-beta2-treated antigen-presenting cells

A growing body of evidence has shown that professional antigen-presenting cells (APC) treated with transforming growth factor-β (TGF-β) can induce a systemic antigen (Ag)-specific tolerance, similar to anterior chamber-associated immune deviation (ACAID). However, the exact mechanism for immune tolerance induced by TGF-β-treated APC has not been elucidated. In this study, we showed that intravenous injection of ovalbumin (OVA)-pulsed APC treated with TGF-β₂ induced a peripheral tolerance as evidenced by an impaired delayed-type hypersensitivity (DTH) response. CD4⁺ T cells from mice receiving an intravenous injection of TGF-β₂-treated APC pulsed with OVA could adoptively transfer a specific tolerance to naïve mice. An increased frequency of FoxP3-expressing CD4⁺ CD25⁺ T cells was observed in mice with tolerance. CD4⁺CD25⁺ T cells from TGF-β₂-treated APC-injected mice produced a large amount of TGF-β₁ and exhibited an in vitro antigen-specific suppressive activity. CD4⁺ CD25⁺ T cells from TGF-β₂-treated APC-injected mice were able to inhibit the antigen-specific DTH response significantly when adoptively transferred to naïve mice. These results indicate that FoxP3-expressing CD4⁺ CD25⁺ T cells might be actively involved in the development of tolerance induced by TGF-β₂-treated APC.     

Decreases in alpha beta T cell receptor negative T cells and CD8 cells, and an increase in CD4+ CD8+ cells in active Hashimoto''s disease and subacute thyroiditis.

We examined peripheral lymphocyte subsets in patients with autoimmune thyroid disease, or subacute thyroiditis, in the active stage when possible. During destructive thyrotoxicosis arising from alpha beta T cell receptor (TCR) negative T (WT31-CD3+) cells and CD8 (CD4-CD8+) cells decreased and those of CD4+CD8+ cells increased slightly, resulting in proportional increases in CD4 (CD4+CD8-) cells, non-T, non-B (CD5-CD19-) cells, and the CD4/CD8 cell ratio. Changes were similar in active subacute thyroiditis. During stimulative thyrotoxicosis in active Graves' disease, the numbers of such T lymphocyte subsets were not changed, but only the number of CD5+ B (CD5+CD19+) cells increased markedly, resulting in proportional decreases in total T (CD3+) cells, alpha beta+ TCR T (WT31+CD3+) cells, CD8 cells, and non-T, non-B cells. A serial study of some of the patients showed opposite changes in alpha beta TCR- T cells, the CD4/CD8 cell ratio, and CD5+ B cells between the active stages of Graves' and Hashimoto's diseases. alpha beta TCR- T cells were mostly gamma delta TCR+ T (IIF2+ CD3+) cells in these patients. These data suggest that alpha beta TCR-T (gamma delta TCR+ T), CD8, and CD4+ CD8+ cells are important in thyroid destruction in Hashimoto's disease and subacute thyroiditis, and that CD5+ B cells are important in thyroid stimulation in Graves' disease.     

Low-dose antigen-experienced CD4+ T cells display reduced clonal expansion but facilitate an effective memory pool in response to secondary exposure

The strength and duration of an antigenic signal at the time of initial stimulation were assumed to affect the development and response of effectors and memory cells to secondary stimulation with the same antigen. To test this assumption, we used T-cell receptor (TCR)-transgenic CD4⁺ T cells that were stimulated in vitro with various antigen doses. The primary effector CD4⁺ T cells generated in response to low-dose antigen in vitro exhibited reduced clonal expansion upon secondary antigenic exposure after adoptive transfer to hosts. However, the magnitude of their contraction was much smaller than both those generated by high-dose antigen stimulation and by naïve CD4⁺ T cells, resulting in higher numbers of antigen-specific CD4⁺ T cells remaining until the memory stage. Moreover, secondary effectors and memory cells developed by secondary antigen exposure were not functionally impaired. In hosts given the low-dose antigen-experienced CD4⁺ T cells, we also observed accelerated recall responses upon injection of antigen-bearing antigen-presenting cells. These results suggest that primary TCR stimulation is important for developing optimal effectors during initial antigen exposure to confer long-lasting memory CD4⁺ T cells in response to secondary exposure.