In vivo and in vitro immune responses of CBA/N (Xid) mice against allogeneic cells.

CBA/N (Xid) mice classically present a genetically determined immune deficiency. This is characterized by the absence of certain B lymphocyte subpopulations (Lyb 3, 5, 7) and a hyporeactivity towards class II T independent antigens. These mice were examined in comparison with conventional CBA/Ca (H-2k) histocompatible controls for their immune reactivity, using different systems linked to allogenic transplantation: the local graft-versus-host reaction (LGVHR), allogeneic tumor (Sa 1 A/J) rejection, mixed lymphocyte reaction (MLR) and cell mediated lymphocytotoxicity (CML). It is concluded that a difference in reactivity is also present in some responses to classically T dependent antigens. This difference can result either in an increased reaction in the case of a primary LGVHR or a decrease in the same but late secondary reaction. The rejection of a tumor allograft (Sa 1 A/J - H-2a) is delayed in the CBA/N (H-2k) substrain with respect to conventional CBA mice. Cell mediated lymphocytotoxicity (CML) does not seem to be affected by the Xid defect in immunized cell donors. On the contrary, MLR responses are strikingly increased. It is suggested that the poor seeding of B cells into peripheral lymphoid organs alters the T/B ratio, favoring either T effector cells or T suppressors (Ts) according to the models used. Antibody responses to allogeneic H-2 antigens are not significantly modified.