T cell response in malaria pathogenesis: selective increase in T cells carrying the TCR V(beta)8 during experimental cerebral malaria.

To characterize the T cells involved in the pathogenesis of cerebral malaria (CM) induced by infection with Plasmodium berghei ANKA clone 1.49L (PbA 1.49L), the occurrence of the disease was assessed in mice lacking T cells of either the alphabeta or gammadelta lineage (TCRalphabeta(-/-) or TCRgammadelta(-/-)). TCRgammadelta(-/-) mice were susceptible to CM, whereas all TCRalphabeta(-/-) mice were resistant, suggesting that T cells of the alphabeta lineage are important in the genesis of CM. The repertoire of TCR V(beta) segment gene expression was examined by flow cytometry in B10.D2 mice, a strain highly susceptible to CM induced by infection with PbA 1.49L. In these mice, CM was associated with an increase of T cells bearing the V(beta)8.1, 2 segments in the peripheral blood lymphocytes. Most V(beta)8.1, 2(+) T cells from peripheral blood lymphocytes of the mice that developed CM belonged to the CD8 subset, and exhibited the CD69(+), CD44(high) and CD62L(low) phenotype surface markers. The link between the increase in V(beta)8.1, 2(+) T cells and the neuropathological consequences of PbA infection was strengthened by the observation that the occurrence of CM was significantly reduced in mice treated with KJ16 antibodies against the V(beta)8.1 and V(beta)8.2 chains, and in mice rendered deficient in V(beta)8.1(+) T cells by a mouse mammary tumor virus superantigen.     

Development of rat CD45+ 13-day-old fetal liver cells in SCID mouse fetal thymic organ cultures.

A phenotypic analysis of the lympho-hemopoietic cells which occur in the liver of 13-day-old fetal rats was achieved by flow cytometry in an attempt to further characterize the rat lymphoid progenitor cells. A small fraction of rat 13-day-old fetal liver (r13FL) cells, which weakly expressed the leukocyte common antigen CD45, constituted a homogeneous Thy-1(hi), CD71(-), CD44(+), MHC class I+, CD43(+) cell subpopulation negative for CD45RC, CD3, TCRalphabeta, TCRgammadelta, CD2, CD5, CD4, CD8, CD25, CD28, NKR-P1a and sIg. On the contrary, the CD45(-) cells were a heterogeneous cell subset which expressed Thy-1, CD71 and CD44 at distinct levels. After MACS separation, the CD45(+) r13FL cells, but not the CD45(-) cell subset, in vitro repopulated 14-day-old SCID mouse fetal thymic lobes providing rat T cells, both TCRalphabeta and TCRgammadelta, NK cells, and thymic dendritic cells but not B lymphocytes. Interestingly, NKR-P1a(lo) TCRalphabeta+ or TCRgammadelta+ cells developed in the xenogeneic cultures, and a rare CD4(+)CD8(+) double-positive subpopulation among the TCRgammadelta-expressing cells accumulated in the oldest cultures. These results are discussed from the double perspective of the nature of the precursor cells which colonize the fetal thymus and the relevance of the xenogeneic SCID mouse fetal thymic microenvironment for supporting rat lymphopoiesis.     

Naturally acquired Pneumocystis carinii pneumonia in gene disruption mutant mice: roles of distinct T-cell populations in infection.

When kept under strict specific-pathogen-free conditions, H-21-Abeta (Abeta(-/-),T-cell receptor beta (TCRbeta(-/-)), and recombinase-activating gene 1 (RAG-1(-/-) gene disruption mutant mice, deficient in conventional CD4+ T cells, TCRalphabeta cells, and all peripheral T and B lymphocytes, respectively, consistently developed lethal Pneumocystis carinii pneumonia through natural infection. The most severe symptoms appeared in RAG-1(-/-) mutants. In contrast, TCRdelta(-/-) and beta2-microglobulin(-/-)(beta2m-/-) mutants, deficient in TCRgammadelta cells and conventional CD8alphabeta+ TCRalphabeta cells, respectively, were fully resistant to infection. Our data indicate not only the insufficiency but also the dispensability of CD8 alphabeta+TCRalphabeta cells and of TCRgammadelta lymphocytes in resistance to P. carinii infection. Under disease conditions, large numbers of unusual single-positive CD4+ and CD8alphabeta+ as well as double-negative TCRgammadelta subpopulations of cells accumulated in lungs of TCRbeta(-/-) mutants. This accumulation was consistently accompanied by a drastic increase in the pulmonary B-cell population. In contrast, CD8alphabeta+ TCR alpha beta cells, but no B cells, appeared in lungs of parasitized Abeta (-/-) mutants. Since lung damage and parasite numbers were less prominent in morbid TCRbeta(-/-) and Abeta(-/-) mutants than in diseased RAG-1(-/-) mice, the remaining lymphocytes accumulating in lungs of the former two mutants seem to perform residual resistance functions.     

Intestinal intraepithelial lymphocytes prevent pathogen-driven inflammation and regulate the Smad/T-bet pathway of lamina propria CD4+ T cells

Intraepithelial lymphocytes (IEL) play a key role in gut homeostasis and are critical effector cells preventing the inflammatory intestinal lesions induced in mice following oral infection with Toxoplasma gondii. In this intestinal inflammatory model, CD4(+) T lymphocytes from the lamina propria (LP) synergize with the infected enterocytes to secrete pro-inflammatory chemokines and cytokines. In this study, we assessed the mechanisms accounting for the ability of IEL to modulate the inflammatory activity of these cells. Adoptive transfer of IEL purified from wild-type mice, or CD154-,CD95L- or IL-10-deficient mice infected with T. gondii completely impairs the development of the lethal ileitis in recipient mice orally infected with T. gondii.Compared with unprimed IEL isolated from naive mice, the CD8 alpha beta TCR alpha beta subset of primed IEL, isolated from T. gondii-infected mice, secretes increased amount of TGF-beta. IEL interact with the LP CD4(+) T lymphocytes, down-regulate their production of inflammatory cytokines such as IFN-gamma and reduce their proliferative activity. These effects are linked to the secretion of TGF-beta and are correlated with a shift in the balance between Smad7/T-bet down-regulation and Smad2/Smad3 up-regulation in LP CD4(+) T lymphocytes.     

The CD94/NKG2C killer lectin-like receptor constitutes an alternative activation pathway for a subset of CD8+ T cells

The CD94/NKG2C killer lectin-like receptor (KLR) specific for HLA-E is coupled to the KARAP/DAP12 adapter in a subset of NK cells, triggering their effector functions. We have studied the distribution and function of this KLR in T lymphocytes. Like other NK cell receptors (NKR), CD94/NKG2C was predominantly expressed by a CD8(+) T cell subset, though TCRgammadelta(+) NKG2C(+) and rare CD4(+) NKG2C(+) cells were also detected in some individuals. Coculture with the 721.221 HLA class I-deficient lymphoma cell line transfected with HLA-E (.221-AEH) induced IL-2Ralpha expression in CD94/NKG2C+ NK cells and a minor subset of CD94/NKG2C(+) T cells, promoting their proliferation; moreover, a similar response was triggered upon selective engagement of CD94/NKG2C with a specific mAb. CD8(+) TCRalphabeta CD94/NKG2C(+) T cell clones, that displayed different combinations of KIR and CD85j receptors, expressed KARAP/DAP12 which was co-precipitated by an anti-CD94 mAb. Specific engagement of the KLR triggered cytotoxicity and cytokine production in CD94/NKG2C(+) T cell clones, inducing as well IL-2Ralpha expression and a proliferative response. Altogether these results support that CD94/NKG2C may constitute an alternative T cell activation pathway capable of driving the expansion and triggering the effector functions of a CTL subset.     

The thymus chapter in the life of gut-specific intra epithelial lymphocytes

The intestinal intraepithelial lymphocytes (IEL) represent multi-lineage T cell populations. In addition to a major gammadeltaTCR(+) T cell subset, many IEL express alphabetaTCRs and they can be separated into alphabeta sublineages. Some TCRalphabeta(+)IEL have characteristics in common with conventional TCRalphabeta(+)T cells whereas others share an unconventional phenotype with their TCRgammadelta(+) counterparts. Because the latter are enriched for autoreactive TCRs and can be generated in the absence of a thymus, it has long been postulated that some IEL subsets develop locally in the intestine. Several new data however, indicate that under physiological conditions, IEL require a thymic education that directs lineage commitment and functional differentiation. This review will discuss the contributions of the thymus in shaping the various intestinal IEL sublineages.     

Functionally active CD8alphabeta+ TCRgammadelta intestinal intraepithelial lymphocytes in athymic nu/nu mice

Murine intestinal intraepithelial lymphocytes (IEL) encompass a high proportion of TCRgammadelta cells. A vast majority of these TCRgammadelta IEL express CD8alpha, but not CD8beta (CD8alphaalpha homodimer), and are considered to develop in intestinal epithelial layers independently of a functional thymus. Here we show that TCRgammadelta cells expressing both CD8alpha and CD8beta (CD8alphabeta heterodimer) appear in athymic nu/nu mice, although their appearance is random. The IEL comprising CD8alphabeta(+) TCRgammadelta cells expressed pronounced cytolytic and IFN-gamma-producing activities after TCRgammadelta ligation, which were markedly stronger than activities of IEL lacking CD8alphabeta(+) TCRgammadelta cells. Purified CD8alphabeta(+) TCRgammadelta cells expressed strong cytolytic activities and produced large quantities of IFN-gamma after TCR engagement. CD8alphabeta(+) TCRgammadelta cells were also identified among IEL from euthymic C57BL/6 mice, although their abundance varied among individual animals. However, cytolytic and IFN-gamma-producing activities in euthymic C57BL/6 mice were markedly lower than those in athymic nu/nu mice. Our findings suggest that CD8alphabeta(+) TCRgammadelta cells can develop in the intestine independently of a functional thymus/thymic epithelial cells and that they perform biological functions in situ.     

Contribution of NK, NK T, gamma delta T, and alpha beta T cells to the gamma interferon response required for liver protection against Trypanosoma cruzi

In the present work, we show that intracellular Trypanosoma cruzi is rarely found in the livers of acutely infected mice, but inflammation is commonly observed. The presence of numerous intrahepatic amastigotes in infected gamma interferon (IFN-gamma)-deficient mice corroborates the notion that the liver is protected by an efficient local immunity. The contribution of different cell populations was suggested by data showing that CD4- and CD8-deficient mice were able to restrain liver parasite growth. Therefore, we have characterized the liver-infiltrating lymphocytes and determined the sources of IFN-gamma during acute T. cruzi infection. We observed that natural killer (NK) cells increased by day 7, while T and B cells increased by day 14. Among CD3+ cells, CD4+, CD8+, and CD4- CD8- cell populations were greatly expanded. A large fraction of CD3+ cells were positive for PanNK, a beta1 integrin expressed by NK and NK T cells. However, these lymphocytes were not classic NK T cells because they did not express NK1.1 and showed no preferential usage of Vbeta8. Otherwise, liver NK T (CD3+ NK1.1+) cells were not increased in acutely infected mice. The majority of PanNK+ CD4+ and PanNK+ CD8+ cells expressed T-cell receptor alphabeta (TCRalphabeta), whereas PanNK+ CD4- CD8- cells were positive for TCRgammadelta. In fact, gammadelta T cells showed the most remarkable increase (40- to 100-fold) among liver lymphocytes. Most importantly, intracellular analysis revealed high levels of IFN-gamma production at day 7 by NK cells and at day 14 by CD4+, CD8+, and CD4- CD8- TCRgammadelta+ cells. We concluded that NK cells are a precocious source of IFN-gamma in the livers of acutely infected mice, and, as the disease progresses, conventional CD4+ and CD8+ T cells and gammadelta T cells, but not classic NK-T cells, may provide the IFN-gamma required for liver protection against T. cruzi.     

Expression and function of NKG2D in CD4+ T cells specific for human cytomegalovirus

The human NKG2D killer lectin-like receptor (KLR) is coupled by the DAP10 adapter to phosphoinositide 3-kinase (PI3 K) and specifically interacts with different stress-inducible molecules (i.e. MICA, MICB, ULBP) displayed by some tumour and virus-infected cells. This KLR is commonly expressed by human NK cells as well as TCRgammadelta(+) and TCRalphabeta(+)CD8(+) T lymphocytes, but it has been also detected in CD4(+) T cells from rheumatoid arthritis and cancer patients. In the present study, we analysed NKG2D expression in human cytomegalovirus (HCMV)-specific CD4(+) T lymphocytes. In vitro stimulation of peripheral blood mononuclear cells (PBMC) from healthy seropositive individuals with HCMV promoted variable expansion of CD4(+)NKG2D(+) T lymphocytes that coexpressed perforin. NKG2D was detected in CD28(-) and CD28(dull )subsets and was not systematically associated with the expression of other NK cell receptors (i.e. KIR, CD94/NKG2 and ILT2). Engagement of NKG2D with specific mAb synergized with TCR-dependent activation of CD4(+) T cells, triggering proliferation and cytokine production (i.e. IFN-gamma and TNF-alpha). Altogether, the data support the notion that NKG2D functions as a prototypic costimulatory receptor in a subset of HCMV-specific CD4(+) T lymphocytes and thus may have a role in the response against infected HLA class II(+) cells displaying NKG2D ligands.     

MHC class II-independent CD25+ CD4+ CD8alpha beta+ alpha beta T cells attenuate CD4+ T cell-induced transfer colitis

CD4+ alpha beta T cell populations that develop in mice deficient in MHC class II (through 'knockout' of either the Aalpha, or the Abeta chain of the I-A(b) molecule) comprise a major 'single-positive' (SP) CD4+ CD8- subset (60-90%) and a minor 'double-positive' (DP) CD4+ CD8alpha beta+ subset (10-40%). Many DP T cells found in spleen, mesenteric lymph nodes (MLN) and colonic lamina propria (cLP) express CD25, CD103 and Foxp3. Adoptive transfer of SP but not DP T cells from Aalpha(-/-) or Abeta(-/-) B6 mice into congenic RAG(-/-) hosts induces colitis. Transfer of SP T cells repopulates the host with only SP T cells; transfer of DP T cells repopulates the host with DP and SP T cells. Anti-CD25 antibody treatment of mice transplanted with DP T cells induces severe, lethal colitis; anti-CD25 antibody treatment of mice transplanted with SP T cells further aggravates the course of severe colitis. Hence, regulatory CD25+ T cells within (or developing from) the DP T cell population of MHC class II-deficient mice control the colitogenic potential of CD25- CD4+ T cells.     

Speculation on the lineage relationships among CD4(-)8(+) gut-derived T cells and their role(s).

The thymus-independent T lymphopoietic capacity of the murine intestinal mucosa has been established. Cryptopatches have now been identified as the location of the elusive precursors for gut-derived T cells. These cryptopatch cells have been shown to give rise to intestinal T cells expressing either TCRgammadelta or TCRalphabeta. Here we discuss the role of MHC in the development and selection of gut-derived T cells. Through the analysis of iIEL selection in animals expressing a transgenic TCRalphabeta, in the presence or absence of p56(lck), we discuss lineage relationships among CD4(-)8(+) iIEL subsets, and their possible function(s).     

Characterization of murine CD160+ CD8+ T lymphocytes

CD160 is an Ig-like glycoprotein expressed on NK, NKT and TCRgammadelta T cells, as well as intestinal intraepithelial T lymphocytes. In addition, a minor subset of CD8(+) but not CD4(+) T cells in the periphery is also known to express CD160, but the subset has not been fully characterized. In this study, we prepared anti-murine CD160 mAbs and investigated the expression profile of CD160 on various subsets of CD8(+) T cells. The amount of CD160 on almost all CD8(+) T cells was increased upon CD3-mediated stimulation in vitro, and soluble CD160 was found to be released. Flow cytometric analysis revealed most CD8(+) T cells expressing CD160 to show a CD44(high) phenotype in vivo. On further analysis, both CD44(high)CD62L(low) effector memory T cells (T(EM)) and CD44(high)CD62L(high) central memory T cells (T(CM)) expressed CD160 at an intermediate level. High levels were evident with recently activated CD8(+) T(EM). Na?ve CD8(+) T cells presumably immediately after stimulation (CD44(low)CD62L(low)CD69(+)) also expressed CD160, but only at a low level. Purified CD160(+) CD8(+) T cells from OT-1 transgenic mice expressing TCR against OVA residues 257-264 presented by H-2K(b) produced IFN-gamma more rapidly than CD160(-) CD8(+) T cells upon antigen stimulation. These results together show that CD160 is expressed on the majority of CD8(+) memory T cells as well as recently activated CD8(+) T cells.     

Regulatory role of mature B cells in a murine model of inflammatory bowel disease

The spontaneous chronic colitis in TCR alpha mutant (TCRalpha(-/-)) mice mediated by CD4(+) TCRalpha(-)beta(+) T cells is more severe in the absence of mature B cells, suggesting a suppressive role of B cells and Ig in the development of chronic colitis. To investigate the direct role of B cells in the suppression of this colitis, cell transfer studies were performed in TCRalpha(-/-) x Igmu(-/-) (alphamu(-/-)) double-knockout mice. The chronic colitis was markedly attenuated in alphamu(-/-) mice after the adoptive transfer of peripheral B cells from TCRalpha(-/-) mice into 3- to 4-week-old alphamu(-/-) mice prior to the development of colitis. Furthermore, transfer of mature B cells from TCRalpha(-/-) mice markedly decreased the number of pathogenic colonic CD4(+) TCRalpha(-)beta(+) T cells in alphamu(-/-) mice with established colitis. This B cell effect required the presence of functional co-stimulatory molecules CD40 and B7-2 (CD86) but not B7-1 (CD80). These results indicate that mature B cells play an important role in the development of chronic colitis in TCRalpha(-/-) mice by directly regulating the pathogenic T cells (CD4(+) TCRalpha(-)beta(+) T cells).     

In situ demonstration of intraepithelial lymphocyte adhesion to villus microvessels of the small intestine

The recirculation of lymphocytes through the intestinal mucosa is important for specific immune defense, but the origin and differentiation of intraepithelial lymphocytes (IEL) are not fully understood. The present study therefore used intravital microscopy to investigate the migration of IEL to the villus mucosa and Peyer's patches of the small intestine. IEL were separated from inverted murine small intestine and mesenteric lymph node (MLN) T cells were also isolated. The adhesion of fluorescence-labeled lymphocytes to postcapillary venules (PCV) of Peyer's patches and arcade microvessels of small intestinal villi was observed after injection. In some experiments, the effect of antibodies against adhesion molecules on cell kinetics were investigated. IEL time-dependently accumulated in villus microvessels of the small intestine, whereas few MLN cells did. Few IEL adhered to the PCV of Peyer's patches. IEL were shown to express alpha(E)beta(7)-integrin but not L-selectin. The accumulation of IEL in villus archade was significantly inhibited by antibody against beta(7)-integrin or mucosal addressin cell adhesion molecules (MAdCAM)-1, but not by alpha(E)-integrin. The combined blocking of beta(7)-integrin and MAdCAM-1 further attenuated the sticking of IEL in this area, although it did not entirely block the IEL adherence. The adherence of CD4(+) or TCRalphabeta IEL to villus microvessels was significantly greater than that of CD4(-) or TCRgammadelta IEL. It was demonstrated in situ for the first time that IEL adhered selectively to the villus microvessels of the small intestine partly via beta(7) and MAdCAM-1.     

Expression and selection of productively rearranged TCR beta VDJ genes are sequentially regulated by CD3 signaling in the development of NK1.1(+) alpha beta T cells

The generation of thymic NK1.1(+)alpha beta T (NKT) cells involves positive selection of cells enriched for V(alpha)14/V(beta)8 TCR by CD1d MHC class I molecules. However, it has not been determined whether positive selection is preceded by pre-TCR-dependent beta selection. Here we studied NKT cell development in CD3 signaling-deficient mice (CD3 zeta/eta(-/-) and/or p56(lck-/-)) and TCR alpha-deficient mice. In contrast to wild-type mice, NK1.1(+) thymocytes in CD3 signaling-deficient mice are approximately 10-fold reduced in number, do not exhibit V(alpha)14-J(alpha)281 rearrangements and fail to express alpha beta TCR at the cell surface. However, they exhibit TCR beta VDJ rearrangements and pre-T alpha mRNA, suggesting that they contain pre-NKT cells. Strikingly, pre-NKT cells of CD3 zeta/Lck double-deficient mice fail to express TCR beta mRNA and protein. Whereas in wild-type NKT cells TCR beta VDJ junctions are selected for productive V(beta)8 and against productive V(beta)5 rearrangements, V(beta)8 and V(beta)5 rearrangements are non-selected in pre-NKT cells of CD3 signaling-deficient mice. Thus, pre-NKT cell development in CD3 signaling-deficient mice is blocked after rearrangement of TCR beta VDJ genes but before expression of TCR beta proteins. Most NKT cells of TCR alpha-deficient mice exhibit cell surface gamma delta TCR. In contrast to pre-NKT cells of CD3 signaling-deficient mice, approximately 25% of NKT cells of TCR alpha-deficient mice exhibit intracellular TCR beta polypeptide chains. Moreover, both V(beta)8 and V(beta)5 families are selected for in-frame VDJ joints in the TCR beta(+) NKT cell subset of TCR alpha-deficient mice. The data suggest that CD3 signals regulate initial TCR beta VDJ gene expression prior to beta selection in developing pre-NKT cells.     

Differential expression of CD43 isoforms on murine T cells and their relationship to acute intestinal graft versus host disease: studies using enhanced-green fluorescent protein transgenic mice.

Three mAb (R2/60, S7 and 1B11) were used to study the expression of murine CD43 on peripheral T cells and intestinal intraepithelial lymphocytes (IEL) from normal mice, and from mice during acute graft versus host disease (GVHD). In the spleen, essentially all T cells expressed the R2/60 and S7 antigens, whereas the 1B11 antigen was expressed on about half of the CD8(+) cells and approximately 15% of CD4(+) T cells. Interestingly, a significant proportion of resting splenic B cells expressed the 1B11 and R2/60 antigens, but not the S7 antigen. The majority of IEL expressed R2/60 antigen; however, the S7 and 1B11 markers were differentially expressed on CD8alpha, CD8beta, TCRalphabeta and TCRgammadelta cells. Immunoprecipitation and Western blotting analyses identified characteristic 115 and 130 kDa reactive components from IEL lysates with mAb S7 and 1B11 respectively, and reactivity to both molecular entities by mAb R2/60. During acute intestinal GVHD induced by injecting CB6F(1) athymic nude mice with spleen cells from C57BL/6 enhanced-green fluorescent protein transgenic mice, 80-90% of donor T cells in the intestine epithelium expressed all CD43 isoforms; however, the level of expression of the 130 kDa CD43 antigen increased significantly and the level of the 115 kDa antigen decreased on GVHD donor T cells compared to cells at the time of transfer. Using EL4 cells, a similar shift in the expression of CD43 isoforms occurred experimentally following treatment with neuraminidase, suggesting that the type of CD43 isoform expressed on T cells is strongly influenced by conditions which affect membrane charge. The significance of these findings for intestinal immunopathology is discussed.     

TcR-alpha/beta(+) CD4(-)CD8(-) T cells in humans with the autoimmune lymphoproliferative syndrome express a novel CD45 isoform that is analogous to murine B220 and represents a marker of altered O-glycan biosynthesis

Autoimmune lymphoproliferative syndrome (ALPS), caused by inherited defects in apoptosis secondary to mutations in genes encoding Fas/CD95/APO-1 and Fas ligand (Fasl)/CD95L, is characterized by nonmalignant lymphadenopathy and splenomegaly, increased T cell receptor alpha/beta(+) CD4(-)CD8(-) T cells (alpha/beta(+) double-negative T cells [alpha/beta(+)-DNT cells]), autoimmunity, hypergammaglobulinemia, and cytokine abnormalities. The alpha/beta(+)-DNT cells are immunophenotypically and functionally similar to alpha/beta(+)-DNT cells that accumulate in lpr and gld mice, which bear genetic mutations in Fas and FasL. In these mice, alpha/beta(+)-DNT cells express the B-cell-specific CD45R isoform B220. We show that alpha/beta(+)-DNT cells of ALPS patients, with either Fas or FasL mutations, also express B220. In addition, also similar to LPR/gLD mice, they have an unusual population of B220-positive CD4(+) T cells. B220 expression, together with our finding of characteristic lectin binding profiles, demonstrates that cell surface O-linked glycoproteins have undergone specific modifications, which may have consequences for lymphocyte trafficking, cell-cell interactions, and access to alternative apoptosis pathways.     

Induction of NK1.1(+) alpha beta TCR(+) T cells by bypassing TCR signals in ZAP-70 deficient mice

The mechanism of development of a unique subset of T cells, thymic NK1.1(+) alpha beta T cells, has been poorly understood. We found that the development of thymic NK1.1(+) alpha beta T cells was defective in mice deficient in ZAP-70. Instead, an accumulation of NK1.1(+) TCR beta(-) NK-like population was detected in the thymus and spleen of the ZAP-70 deficient (ZAP -/-) mouse. In the present report, we examined whether biochemical treatments that replace TCR-mediated positive selection signals could restore the generation of thymic NK1.1(+) alpha beta T cells in ZAP -/- mice using the thymus organ culture. We found that a higher concentration of phorbol ester (PMA) than that required for CD4(+) T cell generation and ionomycin induced the generation of NK1.1(+) alpha beta T cells. Phenotypic analysis of the induced NK1.1(+) alpha beta T cell population suggested that these cells expressed CD8 but not CD4 molecules, which is a different characteristic from ordinary thymic NK1.1(+) alpha beta T cells. These results suggest that differential signaling is required for the generation of mainstream T cells and thymic NK1.1(+) alpha beta T cells.     

Development of T lymphocytes in the nasal-associated lymphoid tissue (NALT) from growing Wistar rats

The aim of the present report was to study the development of several T-lymphocyte subsets in the nasal-associated lymphoid tissue (NALT) of growing Wistar rats. CD5+ and CD4+ lymphocytes gradually increased with age. A predominance of CD8alpha+ over CD4+ T cells was found from 7 to 45 days but from 45 to 60 days of age T helper cells outnumbered the cytotoxic subpopulation. The majority of CD8+ T lymphocytes expressed the heterodimeric isoform. The most relevant findings by immunohistochemistry are: (1) the predominance of TCRgammadelta+ and CD8alpha+ cells at 7 days postpartum over all the other T-cell subpopulations; and (2) that TCRgammadelta+ outnumbered TCRalphabeta+ T cells from 7 to 45 days postpartum whereas alphabeta T cells predominated in 45- and 60-day-old rats. Besides, cytometric studies have shown that the percentages of TCRgammadelta+, CD8alpha+, as well as the population coexpressing both phenotypes (TCRgammadelta+CD8alpha+), were significantly higher in rats at 7 days postpartum when compared to 60 day-old rats. In the present study, the finding of a high number of gammadelta+ and CD8+ T cells early in NALT development may indicate the importance of these subpopulations in the protection of the nasal mucosa in suckling and weaning Wistar rats.