Gerald J. Elfenbein

Defective activation of b5 bearing lymphocytes in rabbits recovering from b5 allotype suppression.

Abstract In b 5 b 5 rabbits recovering from bS allotype suppression there are relatively normal numbers of peripheral blood lymphocytes with endogenously synthesized b5 immunoglobulin on their membrane, but markedly and disproportionately low levels of circulating b5 immunoglobulin. The capacity of peripheral blood cells from these animals to transform into blast cells and synthesize DNA in response to anti-b5 antisera or pokeweed mitogen in vitro is also markedly subnormal. This suggests that the b5 bearing lymphocytes in rabbits recovering from allotype suppression may be unable to give rise to b5 secreting cells due to a functional block of the activation and/or maturation of bone marrow derived (B) lymphocytes.

Proliferation of mouse bone marrow-derived lymphocytes in vitro: One mechanism of response to concanavalin A and phytohemagglutinin

In mixed populations of mouse thymus-derived (T) and bone marrow-derived (B) lymphocytes, both T and B cells proliferate in response to soluble phytohemagglutinin (PHA) and conconavalin A (Con A). We have investigated one mechanism of the B cell proliferative response in vitro to Con A and PHA. Thymocytes (THY) were mitogen pulsed with Con A or PHA and metabolically poisoned with mitomycin C and cycloheximide. Mitogen-pulsed, inhibitor-poisoned THY were used to stimulate relatively pure preparations of B cells. We have shown that T cell surface-bound mitogen itself directly stimulates B cells to proliferate in vitro . In our system T cell surface-bound mitogen is relatively more important than blastogenic mediator production by mitogen coated THY in the stimulation of B cell proliferation. We propose that, in mixed populations of T and B cells cultured with soluble mitogens, mitogen bound to T cell surfaces plays a major role in the stimulation of B cell proliferation.

Appearance of lymphocyte surface markers and functional responses in neonatal and young rabbit spleens.

Abstract We examined spleen cells from newborn to 1-month-old rabbits for easily detectable surface immunoglobulin, complement receptors, and for in vitro proliferative responsiveness to anti-immunoglobulin antisera and several mitogens. From birth through the first month of life about 15% of the cells from rabbit spleens had easily detectable surface immunoglobulin while about 45% had C3 receptors. In adults as many as 77% of the spleen cells had easily detectable surface Ig but the proportion with C3 receptors remained about 45%. The proliferative response to anti-allotype antisera was present at birth, and was at adult levels by 1 month of age. The proliferative response to pokeweed mitogen was low when cells were obtained during the first week of life but was comparable in magnitude to the response of adult cells by 2 weeks of age. In vitro responsiveness to concanavalin A was present at low levels at birth and increased sharply during the first week. We did not observe significant stimulation of spleen cells from neonatal to 4-week-old rabbits by lipopolysaccharide from Salmonella typhosa . Our data suggest that lymphocyte surface markers and functional responses appear asynchronously in spleen cells of developing rabbits.

In vitro proliferation of rabbit bone marrow-derived and thymus-derived lymphocytes in response to vaccinia virus

Abstract Peripheral blood leukocytes from rabbits immunized with vaccinia virus were incubated in vitro with vaccinia antigen, and resultant lymphocyte proliferation was measured by incorporation of tritiated thymidine into acid-insoluble material. Significant lymphocyte stimulation was observed at a time when antiviral antibody was being synthesized in vivo . The extent of proliferation by bone marrow-derived lymphocytes after culture with viral antigen was determined by simultaneous detection of complement receptor lymphocytes (CRLs have been shown to be B cells) and uptake of tritiated thymidine in these CRLs by radioautography. The results indicate that both bone marrow-derived and thymus-derived lymphocytes participate in the in vitro proliferative response of rabbit peripheral blood lymphocytes to vaccinia antigen.