Human Lymphocyte Functional Antigens

Abstract

Following the extensive development of monoclonal antibodies (mAbs) to surface membrane determinants, a variety of surface molecules have been defined on lymphocytes; the expression of some of these molecules helped to define lymphocyte subsets and/or differentiation markers. More recently, some of these surface molecules have acquired a “functional” status: for many of these molecules, their “functional” qualification came as the consequence of the “functional” effects induced in absence of complement, in in vitro assays, by these specific mAbs. Many authors have restricted the qualification of Lymphocyte Functional Antigens (LFA) (1,2) to mAbs able to block CTL lysis in absence of complement. As will be shown, mAbs and therefore the molecules bearing the recognized determinants can induce a variety of agonist and/or antagonist effects on the lymphocytes, which are not restricted to cytolysis. At least, using the following in vitro assays, a number of mAbs were found to interfere with such assays as lectin stimulation, MLR, IL-2 dependent T cell growth, anti-class I or anti-class II cell mediated lympholysis and NK lysis. Other in vitro assays such as lymphokines secretion (IL-2, γ-IFN, etc …), T-B cooperation, can also be studied; we have not used the latter assays routinely. In all cases, however, the major issue raised by these data is the relevance of the observed in vitro phenomenology to in vivo physiology, and the molecular basis of its mechanism.