In vitro Cytotoxic Test for detecting Cell Mediated Immunity to Soluble Antigen

Abstract

THE demonstration that lymphoid cells from immunized donors are cytotoxic for cells carrying antigens to which the cell donor is sensitized has led to the development of in vitro tests for cell-mediated immunity¹. These systems measure directly the lytic activity of “sensitized” lymphocytes, and can be readily adapted to a quantitative approach by incorporating ⁵¹Cr (as sodium chromate) into the antigen-carrying (or “target”) cell, and following the kinetics of target cell destruction by measuring the release of ⁵¹Cr. This approach has been used most effectively in studies of allograft immunity^2,3. But in spite of many obvious advantages, these cytolytic tests are generally applicable only to systems involving cell surface antigens, and as such have found particular use in the study of histocompatibility systems. I now describe attempts to extend the applicability of these systems to antigens which are not an integral part of the cell membrane but which are covalently linked to it by the use of coupling agents. Similar previous attempts^4,5 have only yielded systems of low sensitivity.