Probing a repertoire of T cells responding to a mycobacterial antigen

Abstract

Following infection, Mycobacterium tuberculosis may often persist in host tissues for years. This prolonged interaction may result in a dynamic equilibrium between host and parasite. The situation can be disturbed with reactivation of the infection. Ability to clone T cells and sustain them in long term culture allows the study of T cells in vitro. These studies can be used to understand the nature of the equilibrium between host and parasite. We have studied T cell immunity to M. tuberculosis by using a mycobacterial antigen purified by absorbance to a monoclonal (mab) to raise T cell clones. The mab, TB68, bound to antigenic determinant(s) in all strains of M. tuberculosis and M. bovis BCG and vallee [1]. T cell clones were generated from peripheral blood mononuclear cells (PBMC) of a normal BCG vaccinated individual [2]. Clonality was established by sub-cloning as previously described [3]. Clones of both helper/inducer (leu 1,3⁺, OKT4⁺) and suppressor/cytotoxic (leu 1,2⁺) phenotype were generated and examples of both will be discussed. All of these clones were found to be positive for the antigen recognised by the mab leu 8a. The antigenic specificity of individual clones was determined by co-culturing clone cells with feeders and a variety of antigenic preparations, some of which are known to contain, at least in part, determinants of the eliciting antigen [4].