Immunocompetence of normal human appendiceal lymphoid cells: in vitro studies

In order to study the activity of immunocompetent lymphocytes in normal human adult mucosal lymphoid tissues in the gut, viable mononuclear cells (MNC) from surgically removed appendices were isolated with a rapid and improved technique, and their immune reactivity determined in vitro. Nearly two-thirds of the isolated cells were B cells, composed of sIgM (30%), sIgA (19%) and sIgG (12%), less than one-third of cells being T cells, composed of OKT4+ helper/inducer T cells (18%) and OKT8+ suppressor/cytotoxic T cells (9%). Isolated B cells were responsive to SAC (Cowan type I Staphylococcus aureus) with marked augmentation of IgG production, but not to lipopolysaccharides (LPS). In the presence or absence of pokeweed mitogen (PWM) and protein A, all isotype-specific Ig production was augmented along with increasing ratios of autologous T cells to B cells, whereas in the presence of anti-HLA-DR antibodies the production of IgA and IgM was reduced to a great extent. Finally, in vitro induction of concanavalin A (Con A)-induced suppressor T (Ts) cells was less than that of helper T (Th) cells. Thus, normal adult appendiceal (Ap) lymphocyte reactivity is predominated by helper T (Th) cells; IgA isotype-specific Ig production appears to be largely regulated by the autoreactive Th subset. This responsiveness to exogenous stimuli may play an important role in the gut mucosal immune responsiveness.