[Cellular bases of immunological recognition. Antigen-binding receptors of T-lymphocytes]

The chemical nature, structural peculiarities, immunological specificity of antigen-binding receptors of various T cell subpopulations and the differences of these receptors from the whole Ig molecule were characterized by using a number of techniques, in particular, the selective absorption of T lymphocytes on corresponding target cell monolayers with the following elution of adherent lymphocytes. Participation of H-antigens, Ia-proteins, Ir-gene and Ig V-gene products in processes related to the specific contact of different T subpopulations with an antigen is discussed and a concept on T cell receptors is outlined. According to this concept, receptor active centres of two antigen-recognizing T subpopulations, antigen-reactive cells and effector cell precursors, differ in their nature, being represented by Ir-gene products and V-gene products, respectively. Each of these products is bound to the cell surface with a H-antigen molecule which functions as a constant portion of the receptor in both cell types. These receptors or their subunits freely moving in the cell membrane probably become stabilized during antigen-driven differentiation. This may be accomplished either by combination of several subunits into one multivalent molecule or by replacing the constant part of the receptor molecule by other plasma cell membrane proteins (Ia-proteins in helpers, differentiation antigens in killers). Three steps of the lethal T killer-target interaction are described, as well as the conditions promoting or inhibiting each of these steps. Possible mechanism of disturbance of cell membrane permeability resulting in lysis of target cells are discussed.