CD3γ-independent pathways in TCR-mediated signaling in mature T and iNKT lymphocytes.

Antigen recognition by T-lymphocytes through the T-cell antigen receptor, TCR-CD3, is a central event in the initiation of an immune response. CD3 proteins may have redundant as well as specific contributions to the intracellular propagation of TCR-mediated signals. However, to date, the relative role that each CD3 chain plays in signaling is controversial. In order to examine the roles of CD3γ chain in TCR signaling, we analyzed proximal and distal signaling events in human CD3γ(-/-) primary and Herpesvirus saimiri (HVS)-transformed T cells. Following TCR-CD3 engagement, certain early TCR signaling pathways (ZAP-70, ERK, p38 and mTORC2 phosphorylation, and actin polymerization) were comparable with control HVS-transformed T cells. However, other signaling pathways were affected, such TCRζ phosphorylation, indicating that the CD3γ chain contributes to improve TCR signaling efficiency and survival. On the other hand, CD3γ(-/-) primary invariant NKT cells (iNKT cells) showed a normal expansion in response to alpha-galactosylceramide (α-GalCer) and TCRVß11(bright) iNKT cells were preferentially selected in this in vitro culture system, perhaps as a consequence of selective events in the thymus. Our results collectively indicate that a TCR lacking CD3γ can propagate a number of signals through the remaining invariant chains, likely the homologous CD3δ chain, which replaces it at the mutant TCR.

Differential antibody binding to the surface alphabetaTCR.CD3 complex of CD4+ and CD8+ T lymphocytes is conserved in mammals and associated with differential glycosylation.

We have previously shown that the surface alphabeta T cell antigen receptor (TCR).CD3 complex borne by human CD4(+) and CD8(+) T lymphocytes can be distinguished using mAbs. Using two unrelated sets of antibodies, we have now extended this finding to the surface alphabetaTCR.CD3 of seven additional mammalian species (six non-human primates and the mouse). We have also produced data supporting that differential glycosylation of the two main T cell subsets is involved in the observed TCR.CD3 antibody-binding differences in humans. First, we show differential lectin binding to human CD4(+) versus CD8(+) T lymphocytes, particularly with galectin 7. Second, we show that certain lectins can compete differentially with CD3 mAb binding to human primary CD4(+) and CD8(+) T lymphocytes. Third, N-glycan disruption using swainsonine was shown to increase mAb binding to the alphabetaTCR.CD3. We conclude that the differential antibody binding to the surface alphabetaTCR.CD3 complex of primary CD4(+) and CD8(+) T lymphocytes is phylogenetically conserved and associated with differential glycosylation. The differences may be exploited for therapeutic purposes, such as T cell lineage-specific immunosuppression of graft rejection. Also, the impact of glycosylation on CD3 antibody binding requires a cautious interpretation of CD3 expression levels and T cell numbers in clinical diagnosis.

Cysticercosis in chronic psychiatric inpatients from a Venezuelan community.

Cysticercosis due to Taenia solium infection is endemic in developing countries of the Americas, Asia, and Africa. This study was designed to establish the prevalence of cysticercosis in 158 inpatients of a psychiatric institution in the state of Tachira (Venezuela) and in 127 healthy control subjects. Positive blood tests for cysticercosis by Western blotting were recorded in 18.35% of the patients and in 1.57% of the controls. Individuals with mental retardation were found to carry an increased risk of cysticercosis (RR: 2.92; 1.22 < 2.92 > 7.0; P < 0.05) compared with patients with other psychiatric disorders. Taeniasis by Taenia spp. was not demonstrated in the patient group, although a high incidence of infection by other helminths (95.1%) was detected. The high prevalence of cysticercosis in the psychiatric inpatient group, compared with healthy individuals, and the lack of a differential diagnosis of neurocysticercosis suggest cerebral cysticercosis in a large proportion of these patients. Cysticercosis could be the origin of the psychiatric disorders of these patients and may also be due to contact with the parasite in an environment with poor hygiene conditions and a deficient health care system.

Biochemical differences in the alphabeta T cell receptor.CD3 surface complex between CD8+ and CD4+ human mature T lymphocytes.

We have reported the existence of biochemical and conformational differences in the alphabeta T cell receptor (TCR) complex between CD4(+) and CD8(+) CD3gamma-deficient (gamma(-)) mature T cells. In the present study, we have furthered our understanding and extended the observations to primary T lymphocytes from normal (gamma(+)) individuals. Surface TCR.CD3 components from CD4(+) gamma(-) T cells, other than CD3gamma, were detectable and similar in size to CD4(+) gamma(+) controls. Their native TCR.CD3 complex was also similar to CD4(+) gamma(+) controls, except for an alphabeta(deltaepsilon)(2)zeta(2) instead of an alphabetagammaepsilondeltaepsilonzeta(2) stoichiometry. In contrast, the surface TCRalpha, TCRbeta, and CD3delta chains of CD8(+) gamma(-) T cells did not possess their usual sizes. Using confocal immunofluorescence, TCRalpha was hardly detectable in CD8(+) gamma(-) T cells. Blue native gels (BN-PAGE) demonstrated the existence of a heterogeneous population of TCR.CD3 in these cells. Using primary peripheral blood T lymphocytes from normal (gamma(+)) donors, we performed a broad epitopic scan. In contrast to all other TCR.CD3-specific monoclonal antibodies, RW2-8C8 stained CD8(+) better than it did CD4(+) T cells, and the difference was dependent on glycosylation of the TCR.CD3 complex but independent of T cell activation or differentiation. RW2-8C8 staining of CD8(+) T cells was shown to be more dependent on lipid raft integrity than that of CD4(+) T cells. Finally, immunoprecipitation studies on purified primary CD4(+) and CD8(+) T cells revealed the existence of TCR glycosylation differences between the two. Collectively, these results are consistent with the existence of conformational or topological lineage-specific differences in the TCR.CD3 from CD4(+) and CD8(+) wild type T cells. The differences may be relevant for cis interactions during antigen recognition and signal transduction.