T cell antigens and MHC determinants on rabbit granulocytes

Cross-reaction of a monoclonal antibody to human MHC class II molecules with rabbit B cells

Monoclonal antibodies, 21w4 and 44H10, against human MHC class II determinants, were analysed for their reactivity with rabbit lymphoid cells. Both MAb bind to all human B lymphoblastoid lines, irrespective of their HLA-DR phenotype. HLA-DR antigens, purified by affinity to 21W4 IgG Sepharose, can be precipitated with 44H10 MAb, indicating that both antibodies react with the same molecules. Competitive inhibition studies with purified MAb IgG show that 44H10 and 21w4 recognize different epitopes of HLA-DR molecules. The 21w4 MAb, previously shown to cross-react with cells of pig, mouse and sheep, does not react with rabbit lymphoid cells. The 44H10 MAb binds to lymphoid cell suspensions prepared from rabbit appendix, spleen and mesenteric lymph nodes. Its reactivity correlates with that of RABELA, a polyclonal antibody specific for rabbit B cells. Mesenteric lymph node and spleen cell suspensions, depleted of sIg+ cells, are devoid of 44H10+ cells, while similarly-treated appendix B cells still contain a subset of B cells which are sIg-, RABELA+ and 44H10+. These studies thus report on the presence of MHC class II determinants on rabbit B cells, cross-reacting with human HLA-DR.

Fluorescence-activated cell sorter (FACS) analysis of rabbit cells

Monoclonal antibodies RB1, RB2, RT1, RT2 and RB3 were prepared against rabbit lymphoid cells by immunization with various fractions of rabbit lymphoid cells. The antigens detected by the antibodies are found on B and T cells in different densities. High proportions of polymorphonuclear and bone marrow cells which do not carry the RABELA and RTLA antigens carry the antigens of the RB and RT series. A subpopulation of appendix sIg-negative, RTLA-negative cells has a relatively high concentration of RT2. In general, B and T cells of the appendix show relatively small differences in the membrane densities of RB and RT antigens.

The rabbit immune system: cells regulating the proliferative response of purified T cells to concanavalin A and phytohaemagglutinin

T cell specific, B cell specific and Ia specific polyclonal antisera, as well as monoclonal antibodies, were employed to characterize cells involved in regulation of T cells, proliferating upon stimulation with concanavalin A or phytohaemagglutinin. Evidence for Ia+ accessory cells was obtained and the constellation of membrane antigens was determined by cytotoxic cell kill with the above mentioned antibodies. Help given by Ia+ cells was not blocked by polyclonal antibody against Ia, in the absence of complement. There was indirect evidence that a fraction of helper/accessory cells were Ia-.