Differential infiltration by CD45RO and CD45RA subsets of T cells associated with human heart allograft rejection.

Subsets of T cells express different isoforms of the leukocyte common antigen CD45; those expressing the glycoprotein 220 isoform (CD45RA) have been characterized as naive in their response to antigens, and those expressing the glycoprotein 180 isoform (CD45RO) as memory T cells. The association between the rejection status of human cardiac allograft recipients and the relative infiltration of the CD45 subsets of both CD8+ and CD4+ T cells was examined using two-color immunohistological labeling techniques on 33 heart transplant biopsies, categorized by routine histological and clinical criteria as mild (requiring no treatment) or moderate (requiring antirejection therapy) rejection. Double-labeling was performed using pairs of monoclonal antibodies to define the following populations: CD4+ CD45RA+, CD4+ CD45RO+, CD8+ CD45RA+, and CD8+-CD45RO+. The number of cells per high-power field (HPF) for each of these cell subsets was counted in every biopsy. In cases with mild rejection, infiltration was predominant for CD4+ CD45RA+ cells (median = 5.0 cells/HPF) relative to CD4+ CD45RO+ (3.12 cells/HPF), CD8+ CD45RA+ (2.14 cells/HPF), and especially CD8+ CD45RO+ (1.22 cells/HPF) populations. In cases with moderate rejection, all four subpopulations increased but were essentially equivalent in intensity, such that in comparison to cases with mild rejection, the smallest increase was seen for CD4+ CD45RA+ cells (6.67 cells/HPF, P < 0.09) and the greatest for CD8+ CD45RO+ cells (7.00 cells/HPF, P < 0.002). A majority of CD8 cells expressed CD45RA in 14 of 16 (88%) cases of mild rejection compared to only 2 of 17 cases of moderate rejection. Moreover, the ratio of CD45RO+ to CD45RA+ cells in each biopsy was higher in moderate versus mild rejection for both CD4 (median ratios = 1.13 versus 0.68, respectively; P < 0.008) and CD8 (1.43 versus 0.58, respectively; P < 0.005) subsets. A majority of T cells expressed CD45RO in cases of moderate rejection (11 of 14 or 79%), compared to only 1 of 13 (8%) cases of mild rejection. These findings indicate that during generally self-limited mild acute cardiac allograft rejection there is a predominance of naive CD45RA+ T cells, especially of the CD4 phenotype, whereas during moderate rejection there is a significant shift toward activated CD45RO+ T cells, especially in the CD8 population.     

慢性乙型肝炎患者外周血CD45RA+、CD45RO+T淋巴细胞亚群的特点及临床意义

目的：探讨慢性乙型肝炎患者外周血CD4^＋CD45RA^＋、CD4^＋CD45RO^＋、CD8^＋CD45RA^＋和CD8^＋CD45RO^＋T淋巴细胞亚群的特点及其与肝病病情的关系。方法：采集46例轻中度慢性乙型肝炎患者、58例重度慢性乙型肝炎患者和30例健康人的外周抗凝血，应用流式细胞技术三色荧光分析法对其外周血中CD4^＋CD45RA^＋、CD4^＋CD45RO^＋、CD8^＋CD45RA^＋和CD8^＋CD45RO＋T淋巴细胞亚群进行检测。结果：轻中、重度慢性乙型肝炎患者与正常人相比，其外周血中CD4^＋、CD8^＋T细胞均无明显改变；CD8^＋CD45RA^＋T细胞均明显降低，CD8^＋CD45RO^＋T细胞均明显增高，而CD4^＋CD45RA^＋、CD4^＋CD45RO^＋T细胞均无明显改变；重度慢性乙型肝炎患者与轻中度慢性乙型肝炎患者相比，CD8^＋CD45RA^＋T细胞明显降低（P〈0.05），CD8^＋CD45RO^＋T细胞明显升高（P〈0.05）。结论：乙型肝炎慢性化过程中，CD8^＋CD45RO^＋T细胞起重要作用且与慢性乙型肝炎患者病情的进展呈正相关；检测CD4^＋CD45RA^＋、CD4^＋CD45RO^＋、CD8^＋CD45RA^＋和CD8^＋CD45RO^＋T淋巴细胞亚群比检测CD4^＋和CD8^＋T细胞亚群更能正确、充分、全面地了解慢性乙型肝炎的发病机制和预后，从而有效地指导临床治疗。     

Phenotypic changes associated with activation of CD45RA+ and CD45RO+ T cells.

Resting CD45RO+, mature/memory, T cells are phenotypically distinct from intermediate CD45RO+/CD45RA+ and CD45RA+, immature/virgin, T cells, and are characterized by high levels of expression of a number of adhesion molecules, such as CD2, CD18, CD58 and CD29. The kinetics of up-regulation of molecules, like CD25 and CD54 associated with activation, were similar in both subsets and suggested that their high level expression was associated with later events rather than initial recognition and signal transduction. CD45RA+ T cells, unlike CD45RO+ T cells, were unable to proliferate in response to mitogenic combinations of CD2 monoclonal antibodies (mAb), although in combination with submitogenic doses of PMA both up-regulation of cell-surface molecules and proliferation occurred. In addition, recruitment of CD45RA+ T cells by CD2 mAb-activated CD45RO+ T cells can occur.     

Distribution of Alloreactivity Amongst the CD45 Isoforms of Circulating CD4 and CD8 T Lymphocytes

The expression of different isoforms of the CD45 surface molecule allows lymphocytes to be divided into two nonoverlapping categories, CD45RA and CD45RO. Previous studies of CD4 T cells have shown that responses to soluble antigens are present predominantly in the RO subset and to mitogens in the RA, alloreactivity being present in both subsets. Responses of CD8 T cells have not been investigated in such detail, nor have responses been compared to CD4 cells. Here we report the alloreactive responses of both CD45RA and RO subsets amongst both CD4 and CD8 T lymphocytes. Following isolation of CD4 and CD8 cells with immunomagnetic beads, CD45 subsets were separated by negative depletion using specific monoclonal antibodies. CD45RA populations were greater than 97% pure and CD45RO cells greater than 91%. One-way primary mixed lymphocyte reactions were established using the purified responder cells with irradiated allogeneic peripheral blood mononuclear cells as stimulators; experiments were all repeated at least three times. In assays of CD4⁺ RA and RO subsets, reactivity was present in both isoforms, being consistently, but not significantly, greater amongst the RO subset. With CD8⁺ T cells, reactivity was also present in both isoforms, but was significantly greater in the CD45RA subset, with mean proliferation 2.5–3-fold that of the CD45RO cells ( P  < 0.05).     

CD8+ T-cell subsets defined by expression of CD45 isoforms differ in their capacity to produce IL-2, IFN-gamma and TNF-beta.

Expression of different isoforms of CD45, the leucocyte common antigen (LCA), on T-cell subsets has permitted distinctions between the functional activities of subpopulations within the major CD4+ T-cell subset. With respect to cytokine production, the expression on CD4+ cells of CD45RA, a high molecular weight isoform, defines a population which produces only interleukin-2 (IL-2) and tumour necrosis factor-beta (TNF-beta) in quantity, with peak production of IL-2 occurring after 24-48 hr stimulation, while the CD4+ population bearing high levels of CD45RO, a low molecular weight isoform, can produce a wide range of cytokines within 24 hr of activation. The literature is conflicting on the capacities for cytokine production of CD8+ subsets divided on the basis of either CD45RA or CD45RO expression. The aim of this study was to attempt to clarify this area by determining the amount and kinetics of production of IL-2, interferon-gamma (IFN-gamma) and TNF-beta in CD8+ cells separated on the basis of both CD45RA and CD45RO isoform expression. The results showed that CD8+ CD45RA- and CD8+ CD45RO+ T lymphocytes produce significantly more of all three cytokines than do CD8+ CD45RA+ or CD8+ CD45RO- T cells. The kinetics for IFN-gamma and TNF-beta production were similar for both subsets, while IL-2 production was delayed by approximately 3 hr in the CD8+ CD45RO- population as compared to the CD8+ CD45RO+ subset. It is suggested that some of the confusion over cytokine production by these CD8+ subsets may be attributable to different conditions for isolation causing pre-activation of positively selected populations. It is also suggested that while CD8+ CD45RA+ cells are shown to acquire CD45RO upon activation, as do CD4+ CD45RA+ cells, the results of the present study argue for a different relationship between CD8+ subsets separated on the basis of CD45 isoform expression than between the corresponding CD4+ subsets.     

蕈样肉芽肿患者外周血单一核细胞CD45RA及CD45RO表达的研究

目的探讨蕈样肉芽肿（Mycosis fungoides,MF）患者外周血单个核细胞CD45RA及CD45RO的表达及其与MF发病的关系。方法应用双荧光抗体标记、流式细胞仪检测15例MF患者外周血单个核细胞CD45RA及CD45RO的表达。结果（1）MF患者外周血CD3^＋、CD3^＋CD8^＋细胞与正常对照比较差异不显著（P〉0.05）。（2）MF患者外周血CD4^＋细胞低于正常对照,差异非常显著（P〈0.001）。（3）MF患者外周血T细胞CD3^＋CD4^＋/CD3^＋CD8^＋比值低于正常对照,差异显著（P〈0.001）。（4）MF患者外周血CD45RA^＋细胞低于正常对照,差异非常显著（P〈0.001）,CD45RO^＋细胞高于正常对照,差异非常显著（P〈0.001）。（5）MF患者外周血CD45RO^＋/CD45RA^＋比值高于正常对照,差异非常显著（P〈0.001）。（6）MF患者外周血CD4^＋CD45RA^＋细胞低于正常对照,差异非常显著（P〈0.001）。（7）MF患者外周血CD4^＋CD45RO^＋细胞及CD8^＋CD45RO^＋细胞均高于正常对照,差异非常显著（均P〈0.001）。（8）MF患者外周血CD4^＋CD45RO^＋/CD4^＋CD45RA^＋比值及CD8^＋CD45RO^＋/CD8^＋CD45RA^＋比值均高于正常对照,差异非常显著（P〈0.01及P〈0.001）。结论MF患者外周血中,不仅存在CD4^＋亚群失调和CD4^＋/CD8^＋比值降低,而且在CD4^＋和CD8^＋亚群中也存在CD45RA^＋、CD45RO^＋亚群失调和CD45RO^＋/CD45RA^＋比值升高,从而导致的机体免疫功能紊乱,可能与MF的发病或病情加剧有关。     

Parallel pattern of expression of CD43 and of LFA-1 on the CD45RA+ (naive) and CD45RO+ (memory) subsets of human CD4+ and CD8+ cells. Correlation with the aggregative response of the cells to CD43 monoclonal antibodies.

Human peripheral blood T cells form large aggregates when cultured in the presence of antibodies to the highly sialylated protein CD43. About 25% of the cells in such cultures do not aggregate, however, although virtually all T cells express CD43. To find out if these cells constitute a distinct subpopulation of T cells, we analysed the expression of CD43 and lymphocyte function-associated antigen-1 (LFA-1) and examined the aggregation induced by CD43 monoclonal antibodies (mAb) in CD4+ and CD8+ cells and in their CD45RA+ (naive) and CD45RO+ (memory) subsets, respectively. We found that CD43-stimulated CD8+ cells aggregated more rapidly and formed larger aggregates than CD4+ cells. Furthermore, whereas CD8+CD45RO+ cells formed compact clusters after some hours of incubation, a majority (about 75%) of the CD4+CD45RA+ cells remained as singles even after overnight culture. Flow cytometry analysis showed that the patterns of expression of CD43 and of LFA-1 on the different subsets were strikingly parallel to each other. Thus, CD4+ and CD8+ memory (CD45RO+) T cells expressed higher levels of CD43 than the corresponding naive cells, suggesting that increased levels of CD43 expression are, like LFA-1 expression, a marker of primed or recently activated cells. Immunoprecipitation and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of 125I-labelled subsets showed that CD8+ cells expressed about twice as much CD43 as CD4+ cells. In a particular donor where the mean size of the cells in the four subsets was close to equal, CD4+ memory cells showed a 1.4-fold and CD8+ memory cells a twofold increase in CD43 compared to their corresponding naive populations. The propensity of memory T cells to extravasate may be facilitated by high expression of CD43.     

Age-related modifications of the human alphabeta T cell repertoire due to different clonal expansions in the CD4+ and CD8+ subsets

We have studied the effects of a life-long antigen stimulation on the clonal heterogeneity of human peripheral T cell subsets, as defined by their CD45 isoform expression. CD4+ or CD8+ T cells were obtained from healthy donors ranging in age from 20 to 100 years, and sorted into CD45RA+ and CD45RO+ populations. A modified PCR-heteroduplex analysis was then used to directly compare the TCR Vbeta clonal make up of either compartment pair. We find that the CD4+ T cell repertoire remains largely polyclonal throughout life, since CD4+ expanded clones are rare and accumulate predominantly in the CD45RO+ compartment of exceptionally old donors (100 years old). In contrast, the CD8+ T cell subset contains expanded clones which are already detectable in young adults and become very frequent in 70- to 75-year-old donors in both CD45RA+ and CD45RO+ compartments analyzed. Interestingly, some expanded clones are detectable in the CD45RA+ or in both CD45RA+ and CD45RO+ compartments of either CD4+ or CD8+ T cells. These results indicate that the age-dependent accumulation of expanded clones starts earlier and is more pronounced in the CD8+ than in the CD4+ T cell subset, reinforcing the concept that clonal expansion in the two subsets is controlled by substantially different mechanisms. Furthermore, whereas the finding of expanded CD45RO+ T cell clones is explained by antigen- driven proliferation, the detection of expanded clones in the CD45RA+ or in both CD45RA+ and CD45RO+ compartments would support the hypothesis of reversion from the CD45RO+ to the CD45RA+ phenotype after antigen encounter.      

CD45RO and CD45RA positive cell populations in idiopathic membranous and IgA glomerulopathy.

AIMS: To immunophenotype and quantitate glomerular and interstitial inflammatory cells in cases of idiopathic membranous and IgA glomerulopathy; to correlate cell numbers with aspects of clinical data and renal function. METHODS: Routine indirect immunoperoxidase staining was performed on frozen section renal biopsy specimens for T and B lymphocyte related antigens, macrophages and MHC class II antigens. Double immunohistochemical staining was performed to identify CD45RO+ and CD45RA+ cells. RESULTS: In IgA glomerulopathy correlations were found relating interstitial cell numbers to creatinine concentration at biopsy (CD45RO+ and CD45RA+ cells) and follow up creatinine concentration (CD3+, CD4+, CD8+, CD45RO+, and CD45RA+ cells). Also in IgA glomerulopathy mean arterial pressure at biopsy correlated with interstitial cell numbers and most recent follow up creatinine concentration. There were no correlations between glomerular inflammatory cells and renal function in either disease. Double staining showed that although most glomerular CD45RO+ and CD45RA+ cells were macrophages, positive cells in the interstitium were lymphocytes. The interstitial CD45RO+:RA+ ratio in normal renal biopsy specimens was approximately 5:1; for IgA glomerulopathy it was 1.5 and was 1.0 in idiopathic membranous glomerulopathy. CONCLUSIONS: This study demonstrates that interstitial, and not glomerular, inflammatory cell numbers correlate with renal function in primary glomerular disease and that double staining is necessary to interpret positive immunostaining for antigens located on more than one type of inflammatory cell. Detailed investigation of the interstitial CD45RO+ and CD45RA+ cells may give an insight into the pathogenesis of glomerular disease.     

结直肠癌患者与健康受试者外周血CD45RA+/CD45RO+淋巴细胞表型分析

目的 分析结直肠癌患者与健康受试者外周血CD45RA+/CD45RO+系列T淋巴细胞表达的差异.方法 运用流式细胞术(FCM)检测2010年1月至2013年12月解放军总医院收治的109例结直肠癌患者(试验组)与64例健康受试者(对照组)外周血CD45RA+、CD45RO+、CD4+ CD45RA+、CD4+ CD45RO+T淋巴细胞亚群表达情况,统计分析试验组和对照组性别和年龄的分布是否存在差异,然后进一步分析CD45 RA等T淋巴细胞亚群与结直肠癌临床分期的关系.结果Ⅰ+Ⅱ期、Ⅲ期和Ⅳ期结直肠癌患者外周血CD45 RA+细胞百分率[三者分别为(56.23±7.75)％、(58.86±7.66)％和(59.02±9.71)％]明显高于对照组[(48.94±12.66)％],差异具有统计学意义(F=11.128,P＜0.001);Ⅲ期和Ⅳ期患者的CD45RO+细胞百分率[分别为(47.19±8.30)％和(45.41±10.45)％]则明显低于对照组[(53.43±11.75)％],差异具有统计学意义(F=5.817,P=0.00083);Ⅲ期和Ⅳ期患者CD45RA+/CD45RO+的比值(分别为1.32 ±0.46和1.43±0.63)明显高于对照组(1.00±0.47),差异具有统计学意义(F=6.986,P=0.000185);Ⅰ+Ⅱ期患者CD4+ CD45 RO+细胞百分率[(31.37±6.39)％]明显高于对照组[(27.49±7.19)％],差异具有统计学意义(F=2.368,P=0.009);Ⅳ期患者CD4+ CD45RA+/CD4+ CD45RO+的比值(0.66±0.39)明显高于Ⅰ+Ⅱ期的患者(0.49±0.23),差异具有统计学意义(F=1.812,P=0.029);各组之间CD4+ CD45RA+细胞百分率无明显统计学差异(F=0.637,P=0.592).结论 随着临床分期的增加,结直肠癌患者外周血CD45RA+细胞逐渐增加而CD45RO+细胞逐渐减少,反映出结直肠癌患者随着肿瘤的进展其免疫功能逐渐抑制、逐渐降低的动态过程;CD4+ CD45RA+细胞和CD4+ CD45RO+细胞在反映结直肠癌患者机体免疫功能方面不如CD45RA+细胞和CD45RO+细胞敏感.     

Differential effect of cholera toxin on CD45RA+ and CD45RO+ T cells: specific inhibition of cytokine production but not proliferation of human naive T cells

We have studied how cholera toxin (CT) and its non-toxic cell-binding B-subunit (CTB) affect the activation of pure human T cells in an anti-CD3-driven system. CT, as opposed to CTB, strongly suppressed the proliferative responses as well as cytokine production in CD4+ and CD8+ T cells. CT however, had a differential effect on naive and activated/memory T cell subsets. Costimulation through exogenous IL-2 or through CD28 cross-linking rescued the proliferation of CT-treated naive CD45RA+ T cells, but not of activated/memory CD45RO+ cells. IL-2 production and IL-2 receptor expression were markedly reduced by CT in all T cell fractions, i.e. also in CD45RA+ cells which had maintained proliferative responses. However, the proliferative responses of CT-treated CD45RA+ T cells were IL-2-dependent, as shown by blocking experiments using anti-IL-2 antibodies. These results indicate (i) that CTB has no cytostatic effect on human T cells, (ii) that CT affects proliferation and cytokine production by two different signal pathways, and (iii) that CT might interact with a signal pathway generated through or influenced by CD45.     

Immune abnormalities in aneurysmal subarachnoid haemorrhage patients: relation to delayed cerebral vasospasm

Peripheral blood CD3+, CD19+, CD4+, CD8+ and CD45RO+ mononuclear cell subsets, T-cell proliferative responses to combinations of coimmobilized OKT3 antibody and an ECM protein (collagen I, collagen IV, fibronectin or elastin), and T-cell adhesion to collagen IV, fibronectin and elastin were studied in patients with aneurysmal subarachnoid haemorrhage. No significant difference was found in the major lymphocyte subsets between subarachnoid haemorrhage patients receiving no dexamethasone for brain oedema treatment and healthy blood donors. Compared with the latter, both the dexamethasone-untreated and -treated subarachnoid haemorrhage patients showed decreased relative proliferative responses of circulating T cells to OKT3 combinations with collagen IV and fibronectin, and an increased PHA-activated T-cell adhesion to elastin. CD45RO+, CD4+ and CD19+ peripheral blood cell subsets, CD4+/CD8+ cell ratio, PHA-activated T-cell adhesion to fibronectin and collagen IV, and OKT3-triggered T-cell costimulatory responses to elastin, collagen IV and fibronectin were significantly higher in subarachnoid haemorrhage patients presenting with delayed cerebral vasospasm (DCV) than in their DCV-free counterparts. The DCV-related differences in circulating lymphocyte subsets showed no apparent relationship to the glucocorticoid treatment, whereas the differences in the other indices were confined to the dexamethasone-untreated subarachnoid haemorrhage patients. The above results suggest that the CD4+/CD8+ ratio and T cell-ECM interactions play a role in the emergence of subarachnoid haemorrhage/DCV and may represent potential targets for subarachnoid haemorrhage therapy.     

Phenotypical and Functional Differentiation of CD4+ CD45RA+ Human T Cells Following Polyclonal Activation

Human CD4+ T cells differ in their expression of the leucocyte common antigen. Antibodies detecting certain forms (CD45RA and CD45RO) of this antigen have been used to identify and isolate subpopulations of the CD4+ T cells. These isolated subsets have been shown to have different abilities concerning lymphokine production and provision of help to B cells for Ig production. When these T-cell subsets were activated in vitro with polyclonal activators, the production. When these T-cell subsets were activated in vitro with polyclonal activators, the CD45RA+ cells lost this marker and gained the expression of CD45RO. This was true for all mitogens used in this report, i.e. accessory cell-dependent stimulation with SEA and accessory cell-independent activation with PMA or PHA. A correlation between proliferation and differentiation was observed, but this was probably not causative as stimulation with PMA in the absence of DNA synthesis resulted in the acquisition of CD45RO and loss of the CD45RA antigen. Moreover, cells proliferating vigorously for long periods of time expressed both markers at significant levels, which suggests that proliferation did not automatically result in complete loss of the CD45RA marker. The phenotypical differentiation was associated with a functional differentiation which induced the stimulated cells' ability to act as helper cells for Ig production and to produce gamma interferon (IFN-gamma). The results obtained in this study support the contention that the CD45RA+ cells are precursors of the CD45RO+ cells and that the two subsets represent different maturational stages of the same lineage.     

Immune memory in CD4+ CD45RA+ T cells.

This study addresses the question of whether human peripheral CD4+ CD45RA+ T cells possess antigen-specific immune memory. CD4+ CD45RA+ T cells were isolated by a combination of positive and negative selection. Putative CD4+ CD45RA+ cells expressed CD45RA (98.9%) and contained < 0.1% CD4+ CD45RO+ and < 0.5% CD4+ CD45RA+ CD45RO+ cells. Putative CD45RO+ cells expressed CD45RO (90%) and contained 9% CD45RA+ CD45RO+ and < 0.1% CD4+ CD45RA+ cells. The responder frequency of Dermatophagoides pteronyssinus-stimulated CD4+ CD45RA+ and CD4+ CD45RO+ T cells was determined in two atopic donors and found to be 1:11,314 and 1:8031 for CD4+ CD45RA+ and 1:1463 and 1:1408 for CD4+ CD45RO+ T cells. The responder frequencies of CD4+ CD45RA+ and CD4+ CD45RO+ T cells from two non-atopic, but exposed, donors were 1:78031 and 1:176,903 for CD4+ CD45RA+ and 1:9136 and 1:13,136 for CD4+ CD45RO+ T cells. T cells specific for D. pteronyssinus were cloned at limiting dilution following 10 days of bulk culture with D. pteronyssinus antigen. Sixty-eight clones were obtained from CD4+ CD45RO+ and 24 from CD4+ CD45RA+ T cells. All clones were CD3+ CD4+ CD45RO+ and proliferated in response to D. pteronyssinus antigens. Of 40 clones tested, none responded to Tubercule bacillus purified protein derivative (PPD). No difference was seen in the pattern of interleukin-4 (IL-4) or interferon-gamma (IFN-gamma) producing clones derived from CD4+ CD45RA+ and CD4+ CD45RO+ precursors, although freshly isolated and polyclonally activated CD4+ CD45RA+ T cells produced 20-30-fold lower levels of IL-4 and IFN-gamma than their CD4+ CD45RO+ counterparts. Sixty per cent of the clones used the same pool of V beta genes. These data support the hypothesis that immune memory resides in CD4+ CD45RA+ as well as CD4+ CD45RO+ T cells during the chronic immune response to inhaled antigen.     

CD45 isoform expression during T cell development in the thymus.

Various isoforms of leukocyte common antigen, or CD45, are expressed differentially on T cells at different stages of development and activation. We report studies on CD45 isoform expression on various subsets of human T cells using two- and three-color flow cytometry and cell depletion. Bone marrow cells that were depleted of CD3+ and HLA-DR+ cells were CD45RA-RO-. The earliest CD3-CD4-CD8-CD19- thymocytes were CD45RO- with 20%-30% CD45RA+ cells. The most prominent population of CD4+CD8+ double-positive thymocytes were CD45RA-RO+. Even the CD4+CD8+ blasts were greater than 90% CD45RO+. About 80% of single-positive thymocytes (CD4+CD8- or CD4-CD8+) were also CD45RO+. Only 4.3% of CD4+ and 18% of CD8+ single-positive thymocytes were CD45RA+. In contrast, cord blood T cells which represent the stage that immediately follows single-positive thymocytes, contained 90% CD45RA+ cells. Thus, in terms of CD45 isoform expression, single-positive thymocytes are more like double-positive cells than cord blood T cells. These results suggest the following sequence of CD45 isoform switching during T cell development: CD45RA-RO- or RA+RO- (double-negative thymocytes)----RA-RO+ (double-positive and most single-positive thymocytes)----RA+RO- (cord blood T cells), the last switch from CD45RO to CD45RA occurring as a final step of maturation in the thymus.     

Human CD4+ T cells expressing CD45RA acquire the lymphokine gene expression of CD45RO+ T-helper cells after activation in vitro.

CD4+ T cells were separated into subpopulations according to their expression of different isoforms of the CD45R molecule, i.e. CD45RA and CD45RO. The separated cells were activated with staphylococcal enterotoxin A (SEA) in the presence of formalin fixed Raji cells. Each set of cells was activated twice with a 6-day interval, and the lymphokine gene expression during the first 3 days after initiation of each stimulation was followed by use of polymerase chain reaction (PCR) technology. The lymphokine messenger RNA (mRNA) profiles were found to differ between the subsets, since after the first stimulation the CD45RA+ cells produced mRNA encoding interleukin-2 (IL-2) and IL-1 alpha, whereas the CD45RO+ cells transcribed genes for IL-1 alpha, IL-2, IL-4, IL-5 and interferon-gamma (IFN-gamma). After 6 days of SEA stimulation both populations were mainly CD45RO reactive, and when restimulated displayed the lymphokine mRNA profile restricted to this subset. These results indicate that the CD45RA subset is a precursor of the CD45RO and further strengthen the hypothesis that the former cell population represents naive whereas the latter subset represents memory T cells within the CD4 subset.     

Lymphocyte diversity in a 9-year-old boy with idiopathic CD4+ T cell lymphocytopenia

Since CD4+ lymphocytopenia can be caused by disturbed thymic T-cell maturation, we investigated the T-cell subsets of a 9-year-old boy fulfilling the diagnostic criteria for CD4+ lymphocytopenia in a follow-up period of 4 years. We found (I) reduced CD45RA expression, (II) enhanced CD45RO expression and (III) a significant increase in gamma delta TCR-bearing T cells. An accelerated apoptosis (11%) was observed in the CD45RO+, but not CD45RA+ subset. These findings provide evidence that a disturbed thymic T-cell maturation process might play a role in the pathogenesis of CD4+ lymphocytopenia.     

Deficiency of the expression of CD45RA isoform of CD45 common leukocyte antigen in CD4+ T lymphocytes in children with infantile cholestasis

The immunological background of the pathological changes that appear in infantile cholestasis (infections, inflammatory process in the liver) is largely unknown. With the use of double color flow cytometry, we assessed the distribution of functionally different lymphocyte subpopulations in the peripheral blood of 29 infants with extra and intra-hepatic cholestasis (12 and 17 patients, respectively), aged from 1 to 8.6 months. Control group consisted of 15 age-matched, healthy infants. We examined: (1) the expression of CD3, CD4, CD8, CD19 lymphocyte surface receptors; and (2) the distribution of lymphocyte subsets with distinctive surface Ag characteristics of 'naive' (CD45RA+) and 'memory' (CD45RO+) cells in both CD4+ and CD8+ cell populations. The surface markers expression was evaluated in terms of percentage of positive cells and receptor density. The following changes in the expression of lymphocyte surface markers are described: (1) a decrease in the percentage of total CD3+, CD4+ cells but normal percentage of CD8+ cells and elevated proportion of CD19+ B cells; (2) a reduction of the proportion of 'naive' CD4+ lymphocytes but normal percentage of 'naive' CD8+ as well as 'memory' CD4+ and CD8+ cell subsets; (3) a decrease in density of CD3, CD4+, CD8 receptors, and D45RA isoform in a subset of 'naive' CD4+ cells. We conclude that deficiency of 'naive' CD4+ T cell subset which possess important effector and immunoregulatory functions, and low expression of certain lymphocyte receptors known to be engaged in T cell activation, possibly reflect a defect of cell mediated immunity that may account for viral and bacterial infections, often observed in infants with cholestasis.     

Mucosal T-cell phenotypes in persistent atopic and nonatopic rhinitis show an association with mast cells

Background: Allergic rhinitis is characterized by selective expansion of T cell subsets with a CD4+ phenotype. Recently, we identified a subpopulation of nonallergic rhinitis subjects with increased epithelial mast cell and eosinophil populations, suggestive of local mucosal allergy. Previously, T cell subsets have not been characterized in this subselection of nonallergic subjects and furthermore, their relationship to mast cell and basophil effector cells remain unidentified. Objective: To determine if a subpopulation of nonallergic subjects with idiopathic rhinitis (IR) have localized allergy confined to their nasal mucosa by comparing the T cell subsets and major histocompatibility complex (MHC) II expressing cells to persistent allergic rhinitis (PAR). Furthermore, the relationship between T cell subsets and mast cells/basophils was investigated. Methods: None of the symptomatic patients in this study were clinically allergen‐challenged. Nasal turbinate mucosa was removed from patients with PAR, IR and normal controls. Morphometry was performed on immunostained sections for T cell subset populations including CD3+, CD4+, CD8+, CD25+, CD45RA+, CD45RO+, human leucocyte antigen (HLA)‐DRα (MHC class II), mast cell tryptase and for basophils. Results: Subjects with persistent allergic rhinitis differed to normal controls in showing significantly increased numbers of total (CD3+), activated (CD25+) and allergen‐naïve (CD45RA+) T lymphocytes in their nasal mucosa (P < 0.025). The naïve CD45RA+ memory T cells correlated to mucosal mast cells in PAR (P = 0.03). IR patients differ to allergic subjects in showing significantly reduced numbers of epithelial HLA‐DRα+ cells (P = 0.007), but increased numbers of CD8+ lymphocytes (P = 0.02). The CD8+ T cells correlated with mucosal mast cell numbers (P = 0.02). In both rhinitis groups, basophils were present in very low numbers obviating the need for statistical analysis. Conclusion: PAR is characterized by increased numbers of CD3+, CD25+ and CD45RA+ T lymphocytes compared with normal mucosa. Allergic and nonallergic rhinitis groups can be separated by significant differences in the number of epithelial antigen presenting cells (APCs) (HLA‐DRα+) and sub‐epithelial activated (CD25+) T cells. Moreover, IR patients do not significantly differ to their allergic counterparts with respect to total (CD3+) and naïve (CD45RA+) T cell numbers, or numbers of epithelial activated (CD25+) lymphocytes. IR subjects show significantly increased numbers of CD8+ lymphocytes compared with control mucosa and although our findings suggest that the initiating inflammatory events may differ, both rhinitis groups show a similarity in pathology involving mucosal mast cells with an association to infiltrating T cells.     

Distribution of CD45RA and CD45RO T-lymphocyte subsets in rheumatoid arthritis synovial tissue

We have characterized the lymphocytes in the synovium of patients with rheumatoid arthritis (RA) by immunohistochemistry using monoclonal antibodies directed against B lymphocytes, T lymphocytes, and antibodies directed against CD45RA and CD45RO, which define T-cell subsets. Both CD45RA+ and CD45RO+ T lymphocytes were detected in the perivascular regions. CD45RA+ lymphocytes were present primarily in perivascular areas of moderate to large lymphocytic infiltration. Some synovial perivascular lymphocytic aggregates were organized into focal areas of CD45RA+ B lymphocytes surrounded by CD45RO+ T lymphocytes. In areas of diffuse lymphocytic infiltration, the T lymphocytes were CD45RO+. These data suggest that both CD45RO+ and CD45RA+ T lymphocytes enter the RA synovial tissue via the synovial vasculature and that, once in the tissue, the CD45RA+ T lymphocytes may undergo activation/maturation and acquire the CD45RO phenotype.