The wild-type sequence (wt) p53(25-35) peptide induces HLA-DR7 and HLA-DR11-restricted CD4+ Th cells capable of enhancing the ex vivo expansion and function of anti-wt p53(264-272) peptide CD8+ T cells.

Tumor peptide-based vaccines are more effective when they include tumor-specific Th cell-defined as well as CTL-defined peptides. Presently, two overlapping wild-type sequences (wt) p53 helper peptides, p53(108-122) and p53(110-124), have been identified as HLA-DR1- and/or HLA-DR4-restricted epitopes. These HLA-DR alleles are expressed by approximately 35% of subjects with cancer. To identify Th cell-defined wt p53 peptides suitable for use on the remaining subject population, a dendritic cell (DC)-based coculture system was developed. CD4+ T cells isolated from PBMC obtained from HLA-DR4- normal donors were stimulated ex vivo with autologous DC transfected with wt p53 or mutant p53 cDNA. Reactivity of T cells was tested in ELISPOT IFN-gamma assays against DC pulsed individually with a panel of algorithm-predicted, multiple HLA-DR-binding wt p53 peptides. The wt p53(25-35) peptide was identified as capable of inducing and being recognized by CD4+ T cells in association, at a minimum, with HLA-DR7 and -DR11 molecules, each of which is expressed by approximately 15% of the population. In addition, the presence of anti-p53(25-35) CD4+ Th cells was shown to enhance the in vitro generation/expansion of HLA-A2-restricted, anti-wt p53(264-272) CD8+ T cells, which from one donor were initially "nonresponsive" to the wt p53(264-272) peptide. The wt p53(25-35) peptide has attributes of a naturally presented Th cell-defined peptide, which could be incorporated into antitumor vaccines applicable to a broader population of subjects for whom a wt p53 helper peptide is presently unavailable, as well as used for monitoring anti-p53 Th cell activity in cancer subjects receiving p53-based immunotherapy.

A role for IL-10-mediated HLA-DR7-restricted T cell-dependent events in development of the modified Th2 response to cat allergen.

Although high dose exposure to inhaled cat allergen (Fel d 1) can cause a form of tolerance (modified Th2 response), the T cell mechanism for this phenomenon has not been studied. T cell responses to Fel d 1 were characterized in both allergic (IgE(pos)) and modified Th2 (IgE(neg)IgG(pos)) responders as well as serum Ab-negative controls (IgE(neg)IgG(neg)). Fel d 1 stimulated high levels of IL-10 in PBMC cultures from all individuals, with evidence of Th2 and Th1 cytokine skewing in allergic and control subjects, respectively. Using overlapping peptides, epitopes at the N terminus of Fel d 1 chain 2 were shown to stimulate strong T cell proliferation and to preferentially induce IL-10 (peptide 2:1 (P2:1)) or IFN-gamma (P2:2) regardless of the allergic status of the donor. Injection of cat extract during conventional immunotherapy stimulated expansion of IL-10- and IFN-gamma-producing chain 2 epitope-specific T cells along with increased Fel d 1-specific serum IgG and IgG4 Ab. Six of 12 modified responders expressed the major HLA-DRB1 allele, *0701, and both P2:1 and P2:2 were predicted ligands for this allele. Cultures from DR7-positive modified responders produced the highest levels of IL-10 to P2:1 in addition to other major and minor epitopes within chains 1 and 2. In the presence of anti-IL-10 mAb, both T cell proliferation and IFN-gamma production were enhanced in a Fel d 1- and epitope-specific manner. We conclude that IL-10-producing T cells specific for chain 2 epitopes are relevant to tolerance induction, and that DR7-restricted recognition of these epitopes favors a modified Th2 response.

HLA phenotypes in healthy aged subjects.

One hundred and seventy-one unrelated elderly healthy subjects selected according to the Senieur protocol (57 men and 114 women), aged 75-104 years, and 405 healthy individuals (238 men and 167 women), aged 18-65 years, were typed for HLA-A, HLA-B, and HLA-DR antigens. The purpose of the study was to investigate a possible association between HLA antigens and longevity. In the total group of elderly, an increased frequency of HLA-B16 (11.11 vs. 5.43%) and HLA-DR7 (38.33 vs. 15.67%) and a decreased frequency of HLA-B15 (1.75 vs. 5.18%) and HLA-DR4 (11.66 vs. 24.15%) were observed. The HLA-B15DR4 haplotype was not represented (vs. 2.1%), HLA-A1B8 was found with a low frequency (2.9 vs. 4.4%), and HLA-B8DR3 was very rarely found (1.6 vs. 10.1%), whereas the HLA-B13DR7 haplotype was observed with an increased frequency (6.6 vs. 3.3%). These results are in agreement with other published data and suggest that longevity in humans may be influenced by the genetic background.

B7 but not intercellular adhesion molecule-1 costimulation prevents the induction of human alloantigen-specific tolerance.

Presentation of antigen by the major histocompatibility complex to T lymphocytes without the requisite costimulatory signals does not induce an immune response but rather results in a state of antigen-specific unresponsiveness, termed anergy. To determine which costimulatory signals are critical for the T cell commitment to activation or anergy, we developed an in vitro model system that isolated the contributions of alloantigen and each candidate costimulatory molecule. Here, we show that transfectants expressing HLA-DR7 and either B7 or intercellular adhesion molecule 1 (ICAM-1) deliver independent costimulatory signals resulting in alloantigen-induced proliferation of CD4-positive T lymphocytes. Although equivalent in their ability to costimulate maximal proliferation of alloreactive T cells, B7 but not ICAM-1 induced detectable interleukin 2 secretion and prevented the induction of alloantigen-specific anergy. These results are consistent with the hypothesis that blockade of the ICAM-1:lymphocyte function-associated 1 pathway results in immunosuppression, whereas blockade of the B7:CD28/CTLA4 pathway results in alloantigen-specific anergy. This approach, using this model system, should facilitate the identification of critical costimulatory pathways which must be inhibited in order to induce alloantigen-specific tolerance before human organ transplantation.