Test systems for detection of human T associated Ig-related surface determinants using chicken antiglobulin reagents

In earlier experiments the mixed antiglobulin rosetting reaction (MARR) and the direct antiglobulin rosetting reaction (DARR) were found to be of similar sensitivity in demonstration of immunoglobulin (Ig)-bearing B lymphocytes. These test systems were used in the present study together with chicken anti-F(ab')2, anti-IgM and anti-IgA antibodies to detect Ig-related determinants on human peripheral blood T cells. Although for each antiglobulin reagent the reactivity of viable T cells in the MARR and the DARR appeared to be optimal after treatment of the lymphocytes with neuraminidase, the MARR was always more sensitive than the DARR. Further, when test conditions were established so as to avoid erroneous detection of Ig bound to T cell Fc receptors, the MARR was found to be more sensitive than indirect immunofluorescence. Under the most sensitive mixed antiglobulin rosetting conditions, the mean number of T cells expressing F(ab')2-, alpha- and Mu-related determinants was 99%, 50% and 39% respectively. The complete inhibition of the MARR by human IgM when anti-IgM antibodies are used and the more than 70% inhibition by IgA when anti-IgA antibodies are used, largely exclude false positive rosette formation due to contaminating specificities directed against non-Ig determinants on T cells. Trypsin treatment of T cells removed all determinants recognized by anti-IgM and anti-IgA antibodies and these cells reexpressed these determinants during in vitro culture; this indicates that these determinants are T cell products and do not represent adsorbed Ig molecules.