In vitro and in vivo response of lymphoid cells from LHC hamsters to murine thymus-independent and thymus-dependent antigens.

Lymphoid cell populations (spleen, lymph node, peripheral blood, thymus, and bone marrow) from LHC inbred hamsters were studied in order to characterize further the immune response of this species. The direct PFC response to several thymic-dependent or thymic-independent antigens was evaluated. A specific direct PFC response occurred 4 days after immunization with SRBC, DNP-BSA, DNP-lys-Ficoll, TNP-LPS, TNP-BA, and SSS-III. Attempts to induce a polyclonal antibody response with LPS, TNP-LPS, SSS-III, and DNP-lys-Ficoll were unsuccessful. A weak polyclonal response was induced with TNP-BA. Spleen cells and PBL responded strongly in vitro to the T-cell mitogens Con A and PHA-P, but gave weak and inconsistent responses to the B-cell mitogens LPS and PI-PC. LHC hamster lymphoid cell populations bore sIg and receptors for C3 (EAC rosettes) in approximately the same ratio as various murine species. However, the profile of the number of cells bearing low-to-intermediate densities of sIg differed significantly from those of murine species when analysed with the FACS. There was a sharp reduction in the number of cells with low-to-intermediate densities of sIg. These data suggest that B cells in this strain and species lack the ability to translate signals which lead to polyclonal antibody synthesis or lack the appropriate populations of B cells that have membrane receptors for mitogens which are thought to induce such activity in murine systems and provide evidence for separate signals that induce thymus-independent and mitogenic responses. The importance of this model for studying mechanisms involved in B-cell activation is discussed.