Significantly depressed percentage of CD27+ (memory) B cells among peripheral blood B cells in patients with primary Sjögren's syndrome

CD27 has been found to be expressed on somatically mutated B cells and is thus a positive marker for memory B cells in peripheral blood (PB). Since abnormal immunogloblin (Ig) production is characteristic of the autoimmune diseases primary Sjögren's syndrome (pSS) and rheumatoid arthritis (RA), we have analyzed in detail the CD27 expression on PB B cell from these patient groups. Staining of PB B cells with monoclonal antibodies (MoAb) specific for CD19 and CD27 revealed a significantly depressed percentage of CD27+ PB B cells in patients with pSS (14.8 ± 1.6%) compared to both healthy donors (31.3 ± 4.7%, P = 0.005) and patients with RA (40.8 ± 4.1%, P = 0.0001). In addition, the percentages of both the IgD+CD27+ and the IgD‐CD27+ B‐cell subpopulations were significantly lower in pSS patients compared to RA patients and healthy donors. However, the relative proportion of IgD‐ and IgD+ cells among the CD27+B cells were almost the same for the three groups. Our data suggest a disturbance in the differentiation of peripheral B cells and possibly a bias towards plasma cell differentiation, resulting in a depressed percentage of CD27+ memory PB B cells in pSS. These results are potentially of pathological significance and of diagnostic value.     

Immune system defects in DiGeorge syndrome and association with clinical course

We evaluated 18 DiGeorge syndrome (DGS) patients and aimed to investigate the immunological changes in this population. DGS patients with low naive CD4⁺T and CD8⁺T cells were defined as high‐risk (HR) patients, whereas patients with normal numbers of naive CD4⁺ and CD8⁺T cells were defined as standard risk (SR) patients. Level of serum IgM, CD3⁺ T cell counts and percentages of class‐switched memory B cells were significantly low in HR group compared to SR ones. Severe infections and persistent hypoparathyroidism were detected significantly higher in HR group. Patients with reduced percentages of class‐switched B cells had earlier onset of infection, lower blood IgM, lower CD4⁺ and CD8⁺T counts than patients with normal class‐switched memory B cells. Decreased levels of IgM were associated with low numbers of naive CD4⁺ and recent thymic emigrants T cells. Monitoring the immune changes of patients with DGS would be useful to predict the severe phenotype of disease.     

Hypogammaglobulinemia in children: a warning sign to look deeply?

This study investigated phenotypic and functional characteristics of lymphocytes in children with common variable immunodeficiency (CVID) and unclassified hypogammaglobulinemia (UH), as well as B‐cell subsets in non‐consanguineous parents. Blood samples of 30 children, CVID (n = 9), UH (n = 9), healthy donors HD (n = 12), and 19 adults (parents and controls) were labeled by a combination of surface markers to identify CD4, CD8 T‐cell and B‐cell subpopulations. T‐cell cytokine production in children was analyzed in vitro after stimulation with phytohemagglutinin (PHA) and tetanus toxoid. We observed low percentages of switched memory B cells in children with CVID, increase in total CD4⁺ T‐cell counts, and high percentages of transitional B cells only in UH group. Analysis of T‐cell immunity showed that CVID children had decreased percentages of CD8⁺ IFN‐γ‐producing cells after stimulation with PHA and tetanus toxoid. Parent of children with CVID had low percentages of naive B cell and increased percentages of memory B cells in comparison with controls. These results suggest that (i) early combined immune defect in children with CVID and (ii) a possible familial B‐cell disturbance in pediatric CVID.     

Lymph node and circulating T cell characteristics are strongly correlated in end‐stage renal disease patients,but highly differentiated T cells reside within the circulation

Ageing is associated with changes in the peripheral T cell immune system, which can be influenced significantly by latent cytomegalovirus (CMV) infection. To what extent changes in circulating T cell populations correlate with T cell composition of the lymph node (LN) is unclear, but is crucial for a comprehensive understanding of the T cell system. T cells from peripheral blood (PB) and LN of end‐stage renal disease patients were analysed for frequency of recent thymic emigrants using CD31 expression and T cell receptor excision circle content, relative telomere length and expression of differentiation markers. Compared with PB, LN contained relatively more CD4⁺ than CD8⁺ T cells (P < 0·001). The percentage of naive and central memory CD4⁺ and CD8⁺ T cells and thymic output parameters showed a strong linear correlation between PB and LN. Highly differentiated CD28^null T cells, being CD27^–, CD57⁺ or programmed death 1 (PD‐1⁺), were found almost exclusively in the circulation but not in LN. An age‐related decline in naive CD4⁺ and CD8⁺ T cell frequency was observed (P = 0·035 and P = 0·002, respectively) within LN, concomitant with an increase in central memory CD8⁺ T cells (P = 0·033). Latent CMV infection increased dramatically the frequency of circulating terminally differentiated T cells, but did not alter T cell composition and ageing parameters of LN significantly. Overall T cell composition and measures of thymic function in PB and LN are correlated strongly. However, highly differentiated CD28^null T cells, which may comprise a large part of circulating T cells in CMV‐seropositive individuals, are found almost exclusively within the circulation.     

Emerging role of stem cell memory‐like T cell in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired autoimmune disease characterized by autoantibody‐mediated platelet destruction. Multiple factors have been implicated in ITP pathogenesis, including T‐lymphocyte dysfunctions. Increasing studies have indicated that stem cell memory‐like T cell (TSCM) plays an important role in the development of multiple autoimmune diseases. This study aimed to explore the clinical correlation between the TSCM subset and ITP. The percentages of peripheral blood naïve T cells (TNs), TSCMs, central memory T cells (TCMs), effector memory T cells (TEMs) and effector T cells (TEs) among CD4⁺ and CD8⁺ T cells in 20 ITP patients before and after treatment were detected using flow cytometry. Our results showed that the percentages of peripheral blood CD4⁺ and CD8⁺ T cells in ITP patients were imbalanced. The percentage of CD8⁺ TSCMs in peripheral blood before treatment in ITP patients was significantly higher than that in healthy controls, whereas the percentages of the other T cell subsets did not exhibit significant differences. Our study further analysed the correlation between the change in the percentage of CD8⁺ TSCMs and the treatment efficacy. The results showed that the percentage of peripheral blood CD8⁺ TSCMs in ITP patients after glucocorticoid treatment significantly decreased and the changes of the percentages of CD8⁺ TSCMs before and after treatment in complete response (CR) and response (R) patients were obvious. Our finding showed that the imbalance of the percentage of CD8⁺ TSCMs might be involved in the development of ITP and might serve as a novel indicator of efficacy.     

Inhibition of Alloantigen‐Primed Memory CD4+ and CD8+ T Cells by Hematopoietic Chimerism in Mice

Donor‐reactive memory T cells present a special hurdle in transplantation. Although hematopoietic chimerism is effective for inducing donor‐specific tolerance, the effects on memory T cells are unclear. Here, we induced stable chimerism and tolerance in mice (Tolerance group, n = 6) by donor‐specific transfusion (DST) plus anti‐CD154 monoclonal antibody (mAb), avoiding the toxic myeloablative conditioning treatment to assist bone marrow transplantation (DST/aCD154&BMTx). We then transferred memory CD4⁺ or CD8⁺ T cells from donor antigen primed mice to the tolerance‐induced recipients 4 days after heart transplantation (Tol/CD4⁺ Tm group and Tol/CD8⁺ Tm group, n = 6, respectively), but neither of these memory T‐cell subsets had an effect on the permanent graft survival (median survival time > 100 days). The unaltered rate of memory T cells in spleen and anergy to donor antigen in vitro demonstrated that these memory T cells were well controlled. The chimerism‐promoting protocol DST/aCD154&BMTx produced an immune environment that included high levels of regulatory T cells (Tregs), microchimerism and TGF‐β, all of which may act in suppressing the donor‐reactive memory CD4⁺ or CD8⁺ T cells. These findings have potentially important implications for designing approaches to suppressing memory T cells for success of transplantation.     

Quantification and phenotype of regulatory T cells in rheumatoid arthritis according to Disease Activity Score-28

Here we studied and characterized different peripheral blood (PB) regulatory T cell (Treg) subsets in rheumatoid arthritis (RA) patients and tested the hypothesis that changes in these cells can be linked to the degree of inflammation and relapsing/remission periods. PB cells were examined from RA subjects (n = 60) with different disease activity score-28 (DAS28) and from healthy controls (n = 40). Frequencies of Treg subsets expressing characteristic membrane antigens, FoxP3 or intracellular cytokines were quantified by flow cytometry. We observed a decrease in the percentages of CD4⁺CD25^high, CD4⁺CD25^int, CD4⁺CD25^int/highFoxP3⁺, CD4⁺CD38⁺, CD4⁺CD62L⁺, CD8⁺CD25^highCD45RA⁺ and CD8⁺CD25^intCD45RA⁺ T cells in PB of RA patients compared to healthy controls. In addition, we found increased percentages of cells expressing membrane/intracellular regulatory antigens such as OX40 (CD134), CD45RB^low or CTLA-4 (CD152), and a higher proportion of other T cell subsets including CD4⁺CTLA-4⁺, CD4⁺IL10⁺, CD4⁺CD25^intIL10⁺, CD4⁺CD25^int TGFβ⁺, CD4⁺CD25^low TGFβ⁺ and CD8⁺CD28^? . We show that most of these changes parallel the intensity of inflammation, with lowest or highest values in patients with moderately/very active disease compared to healthy controls and at times to patients with inactive RA. The balance between these cell subsets and their antigen expression would determine the inflammation levels and could thus be linked to the relapsing/remission periods of the disease.     

Increased Numbers ofin vivoActivated T cells in Patients with Recent Onset Insulin-dependent Diabetes Mellitus

Insulin-dependent diabetes mellitus is a T-cell dependent immune mediated disease. Conflicting results regarding the distribution of various T lymphocyte phenotypes in recently diagnosed diabetic patients and in patients with established IDDM compared to controls have been reported. In the present study we evaluated phenotypic characteristics of lymphocytes in IDDM patients. Lymphocytes from 77 newly diagnosed IDDM patients, 58 IDDM patients with disease duration >6 months and 30 non-diabetic controls (including patients with several inflammatory conditions) were analyzed for membrane expression of CD4, CD8, CD45RA, CD45RO and CD27 molecules by FACS analysis. No differences in the percentage of CD8⁺T cells were found between any of the groups. However, the percentage of CD4⁺T cells, and consequently the CD4/CD8 ratio were significantly increased in PBL of recently diagnosed diabetic patients compared to the non-diabetic control group (P<0.005). Interestingly, the fraction of lymphocytes coexpressing CD45RO and CD45RA molecules was significantly increased in recent onset IDDM patients, as well as IDDM patients with disease for a longer duration, compared to controls (P<0.0009 andP<0.007, respectively). IDDM patients had a lower percentage of resting memory T cells (CD45RO⁺CD27⁺) than the non-diabetic controls. The proportion of CD45RO⁺lymphocytes lacking the CD27 molecule ((re)-activated memory cells) was similar in IDDM patients and non-diabetic controls. Our findings confirm and extend previous observations that a disturbance in lymphocyte subset distribution is present in patients with IDDM showing an increase in the percentages of circulating CD4 lymphocytes.     

Fentanyl Suppresses the Survival of CD4+ T Cells Isolated from Human Umbilical Cord Blood through Inhibition of IKKs‐mediated NF‐κB Activation

The aim of this study was to investigate the effects and the underlying mechanisms of fentanyl anaesthetic on T lymphocytes isolated from human umbilical cord blood in vitro. The percentages of CD4⁺, CD8⁺ and regulatory T (Treg) cells in human umbilical cord blood mononuclear cells (UBMC) treated with fentanyl in vitro were analysed by flow cytometry. The levels of cytokines IFN‐γ, IL‐2, IL‐4 and IL‐17 secreted by activated CD4⁺ T cells were measured by ELISA assays. Expressions of MAPK and NF‐κB signalling pathway proteins were determined by Western blotting. Effects of fentanyl on IKK and p65 expression promoter activities were analysed by luciferase assay. Fentanyl decreased the percentages and amounts of CD4⁺, CD8⁺ and Foxp3⁺Treg T lymphocyte subsets in UBMCs in a dose‐dependent manner. Fentanyl inhibited the proliferation and induced apoptosis of activated CD4⁺ T cells dose dependently. Fentanyl could not reverse the increase of cell proliferation in activated groups to be equivalent with those in inactivated group. Secretions of IFN‐γ, IL‐2 and IL‐4 cytokines were significantly decreased by moderate to high dose of fentanyl compared with controls. No significant differences were observed in protein expressions of MAPK pathway. In addition, fentanyl suppressed the IKKs‐mediated activation of NF‐κB. This study demonstrates that fentanyl exerts immunosuppressive effects on T lymphocytes obtained from UBMCs. Thus, the clinical application of fentanyl would not only relieve pain caused by surgery but regulate immune responses post‐operation possibly through inhibition of IKKs‐mediated NF‐κB activation.     

The influence of paediatric HIV infection on circulating B cell subsets and CXCR5+ T helper cells

Antiretroviral therapy (ART) only partially restores HIV‐induced alterations in lymphocyte populations. We assessed B and T cell phenotypes in a cohort of children from a single centre in the United Kingdom with perinatally acquired HIV compared to healthy controls. The majority of HIV infected children (44 of 56) were on fully suppressive combination ART. Children with perinatally acquired HIV had significantly lower memory B and CD4⁺CD45RO⁺CXCR5⁺ [follicular T helper cell (Tfh)‐like] T cell percentages. Detectable viraemia was associated with higher CD21^– (activated and exhausted/tissue‐like memory) B cells. A greater proportion of life spent on suppressive ART was associated with higher memory B cell percentages. These results suggest that early and sustained suppressive ART may preserve B and T cell phenotypes in perinatally acquired HIV and limit deficits in humoral immunity. A lower proportion of circulating Tfh‐like cells in HIV infected children appears to be independent of HIV treatment history and ongoing HIV viraemia and warrants further investigation.     

Partial recovery of senescence and differentiation disturbances in CD8+ T cell effector‐memory cells in HIV‐1 infection after initiation of anti‐retroviral treatment

Immune senescence as well as disturbed CD8⁺ T cell differentiation are a hallmark of chronic HIV infection. Here, we investigated to what extent immune senescence is reversible after initiation of anti‐retroviral treatment (ART). Peripheral blood mononuclear cells (PBMCs) from a cohort of HIV patients with different disease courses, including untreated viral controllers (n = 10), viral non‐controllers (n = 16) and patients on ART (n = 20), were analysed and compared to uninfected controls (n = 25) by flow cytometry on bulk and HIV‐specific major histocompatibility complex (MHC) class I tetramer⁺ CD8⁺ T cells for expression of the memory markers CCR7 and CD45RO, as well as the senescence marker CD57 and the differentiation and survival marker CD127. Furthermore, a subset of patients was analysed longitudinally before and after initiation of ART. Frequencies of CD57⁺CD8⁺ T cells decreased after initiation of ART in central memory (Tcm) but not in effector memory T cell populations (TemRO and TemRA). The frequency of CD127⁺CD8⁺ cells increased in Tcm and TemRO. We observed a reduction of CD127^– T cells in Tcm, TemRO and partially in TemRA subsets after initiation of ART. Importantly, HIV‐specific CD8⁺ TemRO cells predominantly displayed a CD127^–CD57⁺ phenotype in untreated HIV‐patients, whereas the CD127⁺CD57^– phenotype was under‐represented in these patients. The frequency of the CD127⁺CD57^–CD8⁺ T cell subpopulation correlated strongly with absolute CD4⁺ counts in HIV‐infected patients before and after initiation of ART. These findings can be interpreted as a phenotypical correlate of CD8⁺ memory T cell differentiation and the premature ‘ageing’ of the immune system, which was even observed in successfully virally suppressed HIV patients.     

Immunophenotypic characterization of peripheral T lymphocytes in Mycobacterium tuberculosis infection and disease

The cellular immune response probably plays a pivotal role in determining the clinical outcome after exposure to Mycobacterium tuberculosis. We used multi‐parameter flow‐cytometry to evaluate the distribution of T‐lymphocyte subsets during infection and disease caused by M. tuberculosis. Samples were obtained from 71 volunteers to identify the T CD4⁺ and CD8⁺ lymphocyte numbers, and the activation plus memory/naïve phenotypes, as defined by CD38, HLA‐DR, CD45RA and CD27 markers. Subjects were divided into 18 healthy volunteers without detectable reaction to purified protein derivative (PPD^?), 18 health care workers with a recent conversion to PPD, 20 patients with active pulmonary tuberculosis (TBC) and 15 patients with treated TBC at 6 months of therapy. By multiple‐comparison analyses, the T CD4⁺ lymphocyte number of the TBC group was lower than the PPD^– group (P < 0·05). This difference was apparently lost after treatment. The higher and the lower number of naïve T CD4⁺ cells was observed in the PPD^– and TBC group, respectively. CD8⁺ T lymphocytes were also statistically different among the four groups (P = 0·0002), lower in the TBC group (P < 0·05). CD8⁺ T lymphocyte activation was evaluated by the CD38 and HLA‐DR surface expression. The percentage distribution of these markers was statistically different between the four groups (P = 0·0055). TBC patients had a higher percentage of CD38⁺ cells and mean fluorescence index, suggesting an overall increase of cell activation. These results suggest that peripheral T lymphocytes reflect cellular activation during TBC, along with possible redistribution of naïve, memory/effector and late differentiated memory/effector phenotypes in the peripheral blood after infection and disease caused by M. tuberculosis.     

The human immunomodulatory CD25+ B cell population belongs to the memory B cell pool

We have shown that human CD20⁺25⁺ B cells display immunomodulatory properties. The aim of this study was to investigate if CD25⁺ B cells are found within the CD27 memory B cell population, and to analyse pattern of their cytokine production. B cells isolated from healthy subjects, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients were analysed regarding the frequency of CD25⁺ B cells within certain B cell subsets. Purified CD25⁺ B cells from healthy subject were used in vitro to evaluate their production of immunomodulatory cytokines. In healthy subjects the majority (60%) of memory B cells (CD20⁺27⁺) also co‐expressed CD25 while only 10–20% of the naïve B cells (CD20⁺27⁻) and plasmablasts (CD20–27⁺) expressed CD25. In RA and SLE patients, we found that 51% and 48%, respectively, co‐expressed CD25 in the memory population, whereas only 11% and 9% co‐expressed CD25 in the naïve B cell population. Phenotypic analysis of the CD20⁺25⁺27⁺ and CD20⁺25⁺27⁻ cells using CD10, CD24, CD38, CD45, CD71, CD80, CD86, CD95, CD138, BAFF‐R, TACI, IgA, IgD, IgG and IgM showed that CD20⁺25⁺27⁺ B cells preferentially represent highly activated, Ig class switched memory B cells. Cytokine profile analysis showed that CD25⁺ B cells secreted significantly higher levels of IL‐10 versus CD25⁻ B cells. In contrast, TGF‐β1 secretion was similar between the CD25⁺ and CD25⁻ sub‐populations. In conclusion, CD20⁺25⁺ B cells constitute a unique subpopulation preferentially occurring among CD20⁺27⁺ memory B cells. We suggest that CD25 can be used as a marker for a memory B cell subset.     

Persistent low thymic activity and non‐cardiac mortality in children with chromosome 22q11·2 microdeletion and partial DiGeorge syndrome

A subgroup of patients with 22q11·2 microdeletion and partial DiGeorge syndrome (pDGS) appears to be susceptible to non‐cardiac mortality (NCM) despite sufficient overall CD4⁺ T cells. To detect these patients, 20 newborns with 22q11·2 microdeletion and congenital heart disease were followed prospectively for 6 years. Besides detailed clinical assessment, longitudinal monitoring of naive CD4⁺ and cytotoxic CD3⁺CD8⁺ T cells (CTL) was performed. To monitor thymic activity, we analysed naive platelet endothelial cell adhesion molecule‐1 (CD31⁺) expressing CD45RA⁺RO^‐CD4⁺ cells containing high numbers of T cell receptor excision circle (T_REC)‐bearing lymphocytes and compared them with normal values of healthy children (n = 75). Comparing two age periods, low overall CD4⁺ and naive CD4⁺ T cell numbers were observed in 65%/75%, respectively, of patients in period A (< 1 year) declining to 22%/50%, respectively, of patients in period B (> 1/< 7 years). The percentage of patients with low CTLs (< P10) remained robust until school age (period A: 60%; period B: 50%). Low numbers of CTLs were associated with abnormally low naive CD45RA⁺RO^‐CD4⁺ T cells. A high‐risk (HR) group (n = 11) and a standard‐risk (SR) (n = 9) group were identified. HR patients were characterized by low numbers of both naive CD4⁺ and CTLs and were prone to lethal infectious and lymphoproliferative complications (NCM: four of 11; cardiac mortality: one of 11) while SR patients were not (NCM: none of nine; cardiac mortality: two of nine). Naive CD31⁺CD45RA⁺RO^‐CD4⁺, naive CD45RA⁺RO^‐CD4⁺ T cells as well as T_RECs/10⁶ mononuclear cells were abnormally low in HR and normal in SR patients. Longitudinal monitoring of naive CD4⁺ and cytotoxic T cells may help to discriminate pDGS patients at increased risk for NCM.     

Low number of memory B cells in the salivary glands of patients with primary Sjögren's syndrome

We have previously shown that patients with primary Sjögren's Syndrome (pSS) show a significant reduction of autoantigen specific CD27⁺ memory B cells and an abnormally elevated level of autoantibody producing plasma cells in peripheral blood (PB) compared to controls. Because both memory B cells and plasma cells have been detected in salivary glands (SG) of pSS patients, we aimed to study the B cell pattern in SG biopsies. Double immunohistochemical staining of CD20 and CD27 was carried out on paraffin-embedded SG tissue from 10 pSS patients to distinguish CD20⁺/CD27⁺ memory B cells, and identify the CD20⁺ glandular B cell zones (BCZ). Given that plasma blasts and plasma cells are CD27⁺⁺ and CD20^? , additional CD138 single staining of serial sections allowed the distinction of CD27⁺⁺/CD138^? plasma blasts located within the BCZ from CD27⁺⁺/CD138⁺ plasma cells that were found mostly on the periphery of the BCZ and also observed interstitially. Both BCZ and the memory B cell populations were then quantified. Contrary to what has been reported earlier through immunoflourescent staining of memory B cells in SG tissue, we have shown that there is a low number of memory B cells located within the glandular BCZ. Plasma blasts and plasma cells, however, were more abundant in the SG. Together our findings suggest that these low numbers of memory B cells in both PB and SG of pSS patients may be the result of activation of these cells into plasma cells at the site of inflammation.     

Down syndrome, autoimmunity and T regulatory cells

Autoimmune diseases are more represented in Down syndrome (DS) individuals compared to chromosomally normal people. Natural T regulatory cells (nT_reg) have been considered to be primary in the role of controlling the intensity and targets of the immune response. We have investigated the phenotypical and functional alteration of nT_reg in a group of DS people. The phenotypical characteristic of T_reg cells of 29 DS was analysed and compared with an age‐matched healthy control group. The inhibitory potential of CD4⁺CD25^highCD127^low T regulatory cells was evaluated on autologous CD4⁺CD25^‐ T cell proliferation in response to activation with a mytogenic pan‐stimulus (anti‐CD2, anti‐CD3 and anti‐CD28 antibodies). The CD4⁺CD25^high cells in the DS and control groups were 2·692 ± 0·3808%, n = 29 and 1·246 ± 0·119, n = 29%, respectively (P = 0.0007), with a percentage of forkhead box protein 3 (FoxP3)‐expressing cells of 79·21 ± 3·376%, n = 29 and 59·75 ± 4·496%, respectively (P = 0.0015). CD4⁺CD25⁺FoxP3⁺ cells were increased in peripheral blood from DS subjects (DS mean 5·231 ± 0·6065% n = 29, control mean 3·076 ± 0·3140% n = 29). The majority of CD4⁺CD25^high were CD127^low and expressed a high percentage of FoxP3 (natural T_reg phenotype). While the proliferative capacity of DS T cells was not altered significantly compared to normal individuals, a reduced inhibitory potential of T_reg compared to healthy controls was clearly observed (mean healthy control inhibition in T_eff : T_reg 1:1 co‐culture: 58·9% ± 4·157%, n = 10 versus mean DS inhibition in T_eff : T_reg 1:1 co‐culture: 39·8 ± 4·788%, n = 10, P = 0.0075; mean healthy control inhibition in T_eff : T_reg 1:0·5 co‐culture: 45·10 ± 5·858%, n = 10 versus DS inhibition in T_eff : T_reg 1:0·5 co‐culture: 24·10 ± 5·517%, n = 10, P = 0.0177). DS people present an over‐expressed peripheral nT_reg population with a defective inhibitory activity that may partially explain the increased frequency of autoimmune disease.     

Functional deficits of pertussis-specific CD4(+) T cells in infants compared to adults following DTaP vaccination

Understanding the immune responses that explain why infants require multiple doses of pertussis vaccine to achieve protection against infection is a high priority. The objective of this study was to compare the function and phenotypes of antigen‐specific CD4⁺ T cells in adults (n = 12), compared to infants (n = 20), following vaccination with acellular pertussis (DTaP) vaccine. Peripheral blood mononuclear cells (PBMCs) were stimulated with pertussis toxoid (PT), pertactin (PRN) and filamentous haemagglutinin (FHA). Multi‐parameter flow cytometry was used to delineate CD4⁺ T cell populations and phenotypes producing interferon (IFN)‐γ, interleukin (IL)‐2, tumour necrosis factor (TNF)‐α and IL‐4. Based on surface CD69 expression, infants demonstrated activation of vaccine antigen‐specific CD4⁺ T cells similar to adults. However, among infants, Boolean combinations of gates suggested that type 1 (Th‐1) CD4⁺ T cell responses were confined largely to TNF‐α⁺IL‐2⁺IFN‐γ^‐ or TNF‐α⁺IL‐2^‐IFN‐γ^‐. A significantly lower percentage of polyfunctional T helper type 1 (Th1) responses (TNF‐α⁺IFN‐γ⁺IL‐2⁺) and type 2 (Th2) responses (IL‐4) were present in the infants compared to adults. Moreover, a significantly higher percentage of infants' functional CD4⁺ T cells were restricted to CD45RA^‐CCR7⁺CD27⁺ phenotype, consistent with early‐stage differentiated pertussis‐specific memory CD4⁺ T cells. We show for the first time that DTaP vaccination‐induced CD4⁺ T cells in infants are functionally and phenotypically dissimilar from those of adults.     

Atopic asthma: differential activation phenotypes among memory T helper cells

Background T cells have been implicated in the pathogenesis of atopic asthma. We have previously shown that memory T helper cells (CD4⁺CD45RO⁺) are preferentially activated relative to naïve T helper cells (CD4⁺CD45RA⁺) after bronchial allergen challenge. However, specific T helper subpopulations that are activated in atopy and/or asthma remain undefined. Objective To determine the T helper subpopulations and activation phenotypes relevant to acute and stable asthma that may be common with or distinct from atopy. Methods Two groups of atopic asthmatics (ten acute and nine stable asthmatics) and two non‐asthmatic groups (14 non‐asthmatic atopics and eight normal non‐atopic controls) were analysed. Ten acute asthmatics were assessed in the emergency room during an acute episode (FEV₁ 43.6% ± 18.4). Nine stable asthmatics were assessed during a symptom‐free period (FEV₁ 85% ± 6). Using multiple colour flow cytometry we analysed T cell subpopulations and the expression of IL‐2‐receptor (IL‐2R) and MHC‐class II antigens (MHC II) on naïve and memory T helper cells in the peripheral blood of asthmatic and non‐asthmatic groups. Results Atopic asthmatics (acute and stable) had an increased percentage of memory T helper cells expressing IL‐2R compared with normal non‐atopics (mean SD 16.1 ± 6%, 12.4 ± 2% and 7.7 ± 1.8%, P < 0.05) but not compared with non‐asthmatic atopics (10 ± 3.5%). Naïve T helper cells had low expression of IL‐2R and MHC II in all four groups. MHC II antigen expression was increased in memory T helper cells of asthmatics (acute and stable) compared with normal non‐atopics (13.9 ± 7.5, 10.6 ± 5 and 4.9 ± 2.5, P < 0.05) but not compared with non‐asthmatic atopics (7.92 4). A novel finding was that IL‐2R and the MHC II molecules were mainly expressed in non‐overlapping populations and coexpression was found predominantly on memory T helper cells. Asthmatics (acute and stable) had higher proportion of double positive memory T helper cells (IL‐2R⁺MHC II⁺) compared with both non‐asthmatic groups (P < 0.05). Conclusions We demonstrate a differential expression of IL‐2R⁺ and MCH II⁺ on CD45RO⁺ T helper cells that would suggest that there are three subsets of activated memory T helper cells in asthmatics. Two non‐overlapping IL‐2R⁺ or MHC II⁺ CD45RO⁺ T helper cells and a third subpopulation of activated cells that coexpress IL‐2R and MHC II (double positives). This latter subpopulation is significantly higher in asthmatics (acute or stable) compared with both non‐asthmatic groups, suggesting a specific T helper activation phenotype distinct to atopic asthmatics as compared with atopic non‐asthmatics.