Biology Reference
In-Depth Information
Figure 6.2. Generation of CTL.
speci®c antigens are introduced into the body in a nonpathogenic form with the
subsequent development of memory T cells that are capable of developing into
e¨ector cells following secondary contact with the pathogen. In human studies,
the presence of CTL in vivo can be seen by the presence of circulating in vitro
restimulatable antigen-speci®c CTLs following most viral infections (including
HIV ) or vaccinations ( Kourilsky et al., 1998; Schirmbeck et al., 1995).
HIV-speci®c CTL has been shown to exist in most individuals who have
been exposed to the virus. These include children born to infected mothers,
slow, fast, and nonprogressors, and HIV-exposed, uninfected individuals. The
presence of these HIV-speci®c CTL have been shown through ex vivo studies
involving freshly isolated peripheral blood mononuclear cells (PBMC), alveolar
lymphocytes, lymph node biopsies, splenic lymphocytes, and lymphocytes de-
rived from cerebrospinal ¯uid and vaginal secretions (Kaul et al., 2000; Quayle
et al., 1998). A wide range of epitopes (8±11 amino acids) derived from every
surface, structural and regulatory proteins of the HIV, speci®c for di¨erent
human leukocyte antigens ( HLA) have been described (Dadaglio et al., 1991).
Shown in Table 6.1 are the de®ned HIV epitopes, which are restricted to a
single HLA allele, HLA-A2. Even the one allele (of six usually expressed by an
individual) shows a vast range of peptides, although not all are recognized by
the individual ( Betts et al., 2000).
