Biology Reference
In-Depth Information
Antigen Repertoire and Functions of V
d
1 T-Cell Subset in HIV
Infection: Implications for the Immunopathogenesis of AIDS
The antigen speci®city of Vd1 gd T-cell responses in HIV infection is unknown.
Recognition and lysis of B-cell lines obtained from HIV
donors by Vd1 T cells
derived from infected persons have been reported ( Hyjek et al., 1997). Thus,
Vd1 T cells may react to ligands expressed by B cells as a consequence of
their chronic activation during HIV-1 infection. In addition, the diversity of Vg
chain usage, the extensive junctional diversity, and lack of MHC restriction of
the LCL and B-cell-speci®c Vd1 clones in HIV-1-infected individuals suggest a
superantigen-like ligand. Interestingly, infection of T-cell lines with HIV or SIV
induces cell-surface expression of an HSP62 family member and CD50 ( Blast-1
or TCT.1) (Bartz et al., 1994). Consistent with this ®nding, stress-inducible
MICA and MICB molecules are expressed on tumor cells, suggesting that
cellular ligands expressed in states of chronic cellular activation (like tumors
or viral infections) could be recognized by gd T cells. (Ananthan et al., 1986;
Jindal and Malkovsky, 1994).
gd T cells isolated from HIV
donors display cytotoxic activity and secrete
cytokines ( Fig. 8.2). Both Vd1 and Vd2 gd T-cell subsets from humans or
F i g u r e 8.2. Antigen recognition and functions of Vd1 T cells in HIV-1 infection. Vd1 T cells
recognize HIV-1-induced superantigens, B-cell-derived antigens, or MIC antigens (Ag) and undergo
activation and expansion. Vd1 T cells secrete cytokines or display cytotoxic activity. These functions
could have not only an immunoprotective role but also implications in the immunopathogenesis of
HIV-1 disease.
