Differential isotype expression and binding properties of T cell-reactive antibodies in human immunodeficiency virus (HIV) infection.

Isotype and binding characteristics of T cell-reactive antilymphocyte antibodies (ALA) were investigated in 287 human immunodeficiency virus (HIV)+ sera from patients with CDC II to IVC clinical disease. Using purified soluble T-lymphoblast (CEM cell line) membranes and an ELISA method, 29 HIV+ sera showed significant reactions with this substrate and a selective expression of IgG-ALA was detected in 7 HIV+ sera. Subsequent microcytotoxicity assays, utilizing peripheral T lymphocytes and CEM cells as targets, demonstrated no significant cytotoxic capability in such sera, whereas 12 of 17 HIV+ serum samples with IgM-ALA ELISA reactivities showed a significant degree of killing in the Terasaki test. Further experiments of saturation of CD4 molecules on CEM extract by OKT4 monoclonal antibody (MoAb) induced a high inhibition of IgG-ALA binding to the T-cell membranes in only two IgG-ALA+ sera (No. 93, CDC III; No. 179, CDC II stage). Conversely, treatment of CEM membrane lysate with Leu3a MoAb, specific for the gp120 reactive domain of the HIV receptor, failed to prevent membrane binding in all seven of the IgG-ALA+ sera. Following the adsorption of serum 93 on a T-cell membrane antigen affinity column, SDS-PAGE analysis demonstrated that the predominant ALA material reacting with T-cell membranes was IgG with no detectable traces of IgM. These data provide evidence that ALA in HIV+ patients may be simultaneously or selectively expressed as IgG and/or IgM with different properties.(ABSTRACT TRUNCATED AT 250 WORDS)