Appearance Of CD4 Research Articles

Immunohistology of Human Allergic Late-Phase Skin Reactions

Human late-phase allergic skin reactions (LPSR) are characterised histologically by a mixed infiltrate of granulocytes and mononuclear cells. Quantitative immunohistology reveals a correlation between the numbers of CD4+ T-cells and the number of activated eosinophils at LPSR sites. These CD4+ T-cells are predominantly CD45RO+ and belong to the 'memory' T-cell subset. Immunofluorescence studies indicate that type III (immune complex) mechanisms make no significant contribution to the LPSR. On the other hand, the LPSR and classical delayed-type hypersensitivity (DHT) both have a marked CD4+ T-cell component. T-cell infiltration is a more diffuse process in DTH than in the LPSR; between 24 and 48 h, DTH sites show a further increase in T-cell numbers with the appearance of CD8+ T-cells and an influx of monocytes. Activated eosinophils are present in the early stages of both LPSR and DTH, but are more prominent in the LPSR. These different patterns of cellular infiltration and activation are probably due to differences in the cytokine secretion pattern of the infiltrating T-cells. Detailed analysis of this hypothesis will require the use of in situ hybridization techniques.

Sequential Analysis of the Thymocyte Differentiation in Fully Allogeneic Bone Marrow Chimera in Mice. II. Further Characterization of the CD4 + or CD8 + Single Positive Thymocytes

Differentiation of CD4 +8 - and CD4 -8 + single-positive (SP) thymocytes in fully allogeneic bone marrow chimeras were investigated using multicolor cytometric analysis. The proportion of CD3 + cells in CD4 + SP population derived from donor mice considerably increased between day 12 and 14 after bone marrow transplantation (BMT), and gradually increased thereafter. The proportion of V β8 + cells in the CD3 +CD4 + population remained constant (around 20 %) at each period, suggesting that α and β chains were used as TCR. The proportion of J11d + cells in the CD4 + SP thymocytes transiently increased from day 12 to 14 and decreased thereafter, even though almost half of CD4 + SP cells were still dull J11d + at day 35 after BMT. When CD8 + SP populations were analyzed, the proportion of CD3 + cells was very small until day 18. Thereafter, the proportion considerably increased and reached a maximum (83.2 %) at day 21. The proportion of V β8 + cells in the CD3 + CD8 + SP population fell within range between 20 and 30 %. However, before day 18, most of the V β8 + cells were dull positive, while after day 21 the majority were bright V β8 +. Further, CD8 + SP cells at day 12, 14 and 18 were largely bright J11d +. After day 21, however, the proportion of bright J11d + cells rapidly decreased. Similar results were obtained when the sequence of appearance of CD4 + and CD8 + SP cells was compared among bright CD3 +, bright V β8 + or J11d - mature populations. The CD4 + SP cells regularly appeared earlier than CD8 + SP cells in the mature populations. These findings indicate that a considerable heterogeneity exists within both CD4 + and CD8 + SP populations and that the differentiation process for CD4 + SP cells precedes that for CD8 + SP cells.

Delayed thymocyte maturation in the trisomy 16 mouse fetus.

Abstract Mouse fetuses with trisomy 16, an animal model for human trisomy 21 (Down syndrome), have severe defects in several hematopoietic stem cell populations and a marked reduction in thymocyte number. To determine whether there are other defects in the development of the trisomic thymus, the ontogeny of the cell surface antigenic determinants, Thy-1, Ly-1, CD3, CD4, CD8, and TCR v beta, was investigated. The trisomy 16 thymocytes were able to express all of determinants either during fetal life (days 14 to 19 of gestation) or in cultures of intact thymus lobes. However, in all instances (except for Thy-1, which already had a high proportion of expressing thymocytes by day 14), there was a delay in the time at which the determinants were first expressed, as manifested by reduced numbers of positively staining cells. Furthermore, there was also a delay in the rate at which the positively staining cells attained maximal Ag densities. Overall, there was an approximate 2 day lag in development of the fetal trisomic thymocytes. This lag permitted the identification of a large population of CD4-8+ cells prior to the appearance of CD4+8+ thymocytes. These findings are consistent with the identification of CD4-8+ as an intermediate stage between CD4-8- and CD4+8+ in fetal thymocyte ontogeny.

Gamma Interferon Induces the Appearance of a CD4‐, Major Histocompatibility Complex Class II+ Macrophage Subpopulation in the Rat Peritoneal Cavity

Peritoneal cells from gamma interferon (IFN-gamma)-treated rats were phenotypically characterized by flow cytometry. Intraperitoneal inoculation of 3 x 10(4) units of IFN-gamma induced, within 24 h, the appearance of a CD4-, major histocompatibility complex (MHC) class II+ macrophage subpopulation not present in rats treated with phosphate-buffered saline. IFN-gamma induced an increased expression of MHC class II I-A molecules on both CD4- and CD4+ macrophages. Both cell types adhered to plastic and expressed high levels of the macrophage membrane molecules CD11b and OX41. Histological examination of sorted CD4- and CD4+ macrophages confirmed the macrophage morphology of both populations with less granula in the former. We conclude that the appearance of CD4- macrophages in the peritoneal cavity after inoculation with IFN-gamma most probably reflects a selective recruitment of these cells from blood or surrounding tissues. The function of these cells is still unknown, although strong expression of MHC class II I-A indicates competence as antigen-presenting cells.

Expression of ets genes in mouse thymocyte subsets and T cells.

The cellular ets genes (ets-1, ets-2, and erg) have been identified by their sequence similarity with the v-ets oncogene of the avian erythroblastosis virus, E26. Products of the ets-2 gene have been detected in a wide range of normal mouse tissues and their expression appears to be associated with cell proliferation in regenerating liver. In contrast, the ets-1 gene was previously shown to be more highly expressed in the mouse thymus than in other tissues. Because the thymic tissue contains various subsets of cells in different stages of proliferation and maturation, we have examined ets gene expression in fetal thymocytes from different stages of development, in isolated subsets of adult thymocytes, and in peripheral T lymphocytes. Expression of the ets-1 gene was first detected at day 18 in fetal thymocytes, corresponding to the first appearance of CD4+ (CD4+, CD8-) thymocytes, and reaches maximal/plateau levels of expression in the thymus at 1 to 2 days after birth. The ets-2 gene expression is detected at least 1 day earlier, coinciding with the presence of both double-positive (CD4+, CD8+) and double-negative (CD4-, CD8-) blast thymocytes and reaches maximal/plateau levels 1 day before birth. In the adult thymus, ets-1 and ets-2 mRNA expression is 10- to 8-fold higher respectively in the CD4+ subset than in the other subsets examined. Higher levels of p55 ets-1 protein were also shown to exist in the CD4+ subset. Because the CD4+ thymic subset is the pool from which the CD4+ peripheral, helper/inducer T cells are derived, the ets gene expression was examined in lymph node T cells. Both the CD4+ and the CD8+ T cells subsets had lower ets RNA levels than the CD4+ thymocytes. These results suggest that ets-2 and more particularly ets-1 gene products play an important role in T cell development and differentiation and are not simply associated with proliferating cells, which are observed at a higher frequency in fetal thymocytes, or dull Ly-1 (low CD5+), and double-negative (CD4-, CD8-) adult thymocytes. Selectively enhanced expression of ets-1 gene may be observed in thymic CD4+ thymocytes because these cells have uniquely encountered MHC class II or other Ag in the thymic environment. These cells may have been subsequently stimulated to activate the ets genes in conjunction with their differentiation of helper/inducer function(s) and expression of mature TCR.(ABSTRACT TRUNCATED AT 400 WORDS)

Thymocytes expressing CD8 differentiate into CD4+ cells following intrathymic injection.

Based on the cell surface expression of CD4 and CD8 molecules, murine thymocytes can be divided into four populations: these include CD4-, CD8- double-negative and CD4+, CD8+ double-positive subpopulations, both of which consist largely of immature cells, and the single positive, CD4+ or CD8+, subsets that contain functional helper or killer cells, respectively. The double-negative subset contains precursors of the other three populations and can reconstitute the thymus following intravenous or intrathymic transfer into irradiated hosts. In an attempt to establish the sequence of CD4 and CD8 expression during intrathymic development, we investigated the differentiation potential of highly purified CD8+ thymocytes by using intravenous or intrathymic adoptive transfer. Unlike the double-negative thymocyte subset, CD8+ cells did not have the ability to home to the thymus following intravenous transfer. However, when CD8+ thymocytes were injected directly into the thymus, they increased in number and gave rise to CD4+, CD8+ double-positive and CD4+ single-positive progeny. Furthermore, the rate of appearance of CD4+ cells from injected CD8+ precursors was faster than from the double-negative subset. Cells expressing a high surface density of CD8 convert to double-positive and CD4+ progeny without increasing in number, whereas CD8+ cells expressing a low surface density of the marker expand greatly and give rise to differentiated progeny. The results suggest that CD8 expression is an intermediate step on the differentiation pathway of mature CD4+ T cells.

M. leprae and PPD-triggered T cell lines in tuberculoid and lepromatous leprosy.

Proliferative responses of peripheral blood mononuclear cells (PBMC) to Mycobacterium leprae and bacillus Calmette Guerin-derived purified protein derivative (PPD) were studied in the presence or absence of interleukin 2 (IL 2) in high M. leprae responders (tuberculoid leprosy patients and healthy subjects) and low M. leprae responders (lepromatous leprosy patients). High responders in most cases developed a strong proliferative response to both antigens in the absence of IL 2. Additional IL 2 and restimulation with antigen plus autologous antigen-presenting cells (APC) allowed the derivation of antigen-specific T cell lines. The lines were assayed for proliferative responses to several mycobacterial antigens. Both PPD and M. leprae-triggered T cell lines exhibited a good proliferative response to either antigen and showed in addition a broad cross-reactivity with other mycobacteria, suggesting a preferential T cell response to epitopes shared by several mycobacterial species. Within the lepromatous group, 50% of the patients studied could mount a proliferative response to PPD antigen in the absence of IL 2, but none of them was able to do so with M. leprae antigen. The addition of IL 2 increased the number of positive responders to PPD in this group, and in some patients IL 2 was able to restore M. leprae reactivity as well, suggesting that IL 2 had overcome a suppressor mechanism. PPD and M. leprae-triggered T cell lines were obtained from these subjects (with IL 2 added from the beginning of the culture when required). M. leprae lines exhibited variable and unstable pattern of specificity, most lines exhibiting, at least transiently, a cross-reactive response to other mycobacteria, but some displaying only M. leprae-specific response. In contrast, PPD lines from these subjects consistently exhibited a good response to PPD, a lesser response to various other mycobacteria and no response to M. leprae, a pattern differing from that obtained with PPD lines of high M. leprae responders. Co-cultures of irradiated lepromatous PPD triggered T cell lines with fresh autologous PBMC non-specifically reduced the proliferative response of the latter to PPD, as well as to unrelated antigens. A similar suppression was also observed when PPD lines from one of the tuberculoid patients were assayed. PPD and M. leprae T cell lines from both high and low responders initially exhibited the same CD4+ CD8- phenotype. In all cases, antigenic specificity declined and could not be maintained after 5 to 8 wk of continuous culture, a change associated with the progressive appearance of CD8+ and Leu8+ cells.