A factor from CD8 cells of human immunodeficiency virus-infected patients suppresses HLA self-restricted T helper cell responses.

Defective in vitro T helper cell (Th) function can occur in asymptomatic human immunodeficiency virus (HIV)-seropositive (HIV+) individuals. A characteristic, early finding is the loss of an in vitro response to recall antigens, such as influenza A virus (FLU), despite an intact Th response to alloantigen (ALLO). To determine whether suppressor cells and/or inhibitory factors could contribute to this HIV-associated Th immunodeficiency, coculture studies were performed using peripheral blood leukocytes (PBLs) from monozygotic twins, one of whom was HIV-infected (HIV+) and one of whom was uninfected (HIV-seronegative, HIV-). In vitro Th function was measured as interleukin 2 production or proliferation to FLU and ALLO. Two pairs of twins were repetitively studied. A single HIV+ individual with multiple samples of cryopreserved PBLs over 6 years (including a HIV- specimen) was also studied. PBLs from the HIV+, but not from the HIV-, individuals demonstrated defective in vitro Th function in response to FLU but not to ALLO. PBLs from HIV+ individuals could induce a similar defect in the Th function of syngeneic or autologous HIV- PBLs. This suppression was generated by CD4-depleted, but not by CD8-depleted, PBLs. A suppressive factor from CD8+ cells of HIV+ donors was generated by 24-hr unstimulated cultures of HIV+ PBLs. This factor inhibited FLU but not ALLO responses of autologous, syngeneic, or allogeneic HIV- PBLs. This suppressive effect could not be explained by HIV infection or replication during the culture period. These results demonstrate that selective abrogation of Th function to recall antigens in HIV+ individuals is associated with an inhibitory factor produced by CD8+ T cells.