Influence of monoclonal antibodies against HLA class I and class II antigen on interferon-gamma and -alpha induction

Functional effects of a monoclonal antibody directed against a distinct epitope on 4F2 molecular complex in human peripheral blood mononuclear cell activation

The 4F2 antigenic complex is expressed on most human cell lines in culture, on monocytes and activated lymphocytes, but not on resting T and B lymphocytes. Monoclonal antibody (mAb) CB43 recognizes an epitope of the 4F2 heterodimer either located on the light chain or dependent on the conformation of the molecule. The binding of CB43 mAb to peripheral blood mononuclear cells (PBMC) induced a dose-dependent comitogenic effect in the presence of submitogenic concentrations of anti-CD3 mAb. Significant amounts of interleukin (IL)-1 beta but not IL-2 or interferon-gamma were released in the supernatant. Pretreatment of monocytes with CB43 mAb increased the phytohemagglutinin-induced T lymphocyte proliferation. However, CB43 mAb did not exert agonistic effects on activated T lymphocytes. Depletion of CB43+ cells from PBMC decreased the proliferation and generation of cytotoxic effector cells induced by a mannoprotein (MP) derived from Candida albicans cell wall but not by recombinant IL-2. Furthermore, depletion of CB43+ cells from PBMC preactivated with MP or rIL-2 led to a significant decrease in their cytotoxic activity. CB43 mAb did not inhibit the growth of cell lines nor the proliferation of T cells. Thus CB43 mAb identifies a distinct functional epitope on the 4F2 molecular complex and might be useful in further studying the role of this molecule in cellular activation.

Differences in the mechanism of induction of interferon-alpha by herpes simplex virus and herpes simplex virus-infected cells

The cellular source of IFN alpha after induction with Herpes simplex virus type-1 (HSV) and HSV-infected fibroblasts was investigated by using human peripheral blood mononuclear cell (PBMC) populations, purified according to conventional procedures, and which included T- and B-lymphocytes as well as monocytes. It appears that the cells responding to HSV virions are monocytes, whereas the PBMC population induced by HSV-infected cells is represented by B-lymphocytes. Furthermore, by using monoclonal antibody (MoAb) to HLA class I and class II products, it appears that different membrane structures are involved in the induction of IFN by HSV virions, as opposed to HSV-infected cells. In fact, most anti-HLA class II MoAbs inhibit IFN induction by HSV-infected cells, and not IFN induction by HSV virions.

Mechanism of human interferon-gamma production: involvement of beta-2-microglobulin

The ability of several monoclonal antibodies (MoAbs) against beta-2-microglobulin (beta 2m) to inhibit interferon-gamma (IFN) production was assayed in peripheral blood mononuclear cells (PBMC). All of them strongly reduce IFN-gamma induction by galactose oxidase (GO), a well-characterized enzyme capable of activating T lymphocytes through mediation of macrophages. In contrast, many MoAbs directed against HLA class I (heavy chain) and class II antigens do not inhibit IFN induction by GO. On the other hand, anti-beta 2m MoAbs do not effectively reduce IFN-gamma induction by A23187, a calcium ionophore that acts on T cells in the absence of accessory cells. Competition experiments demonstrate that (i) the inhibition of anti-beta 2m antibodies was specific for beta 2m protein, and (ii) beta 2m is not itself the site of action of GO. Moreover, it is demonstrated that the addition of beta 2m to oxidated PBMC strongly enhances subsequent IFN-gamma production. Oxidation of galactose residues on glycoproteins of macrophage membrane is an obligate step for IFN-gamma induction whatever the inducer, thus our results suggest that beta 2m is involved in the mechanism of induction of IFN-gamma.