IL-2 AND IL-3 PRODUCTION IN HIGH AND LOW IGG-RESPONDING STRAINS OF MICE

The antibody response of mouse strain C57B1/10ScSn (B10) is characteri zed by a low IgG responsiveness to a number of different antigens. Abe rrant function of antigen-presenting cells and/or low activity of the Th cell population have been suggested as the cause of the defect. We studied the production of IL-2 and IL-3 in vitro by unstimulated and C onA-stimulated spleen cells. Unstimulated spleen cells of low-respondi ng BIO mice produce significantly less IL-2 compared with the high-res ponding A/J mice in both intervals tested, i.e. after 24 and 48 h of i n vitro incubation. IL-3 production is low but almost comparable in un stimulated cells of both strains. Stimulation of spleen cells by 5 mug /ml of ConA leads to considerably higher production of IL-2 in A/J spl een cells. IL-3 production by ConA-stimulated spleen cells showed the same pattern of activity. This low IL-3 production by B10 cells is mos t likely due to the low production of IL-2 during Th cell activation a nd to the limited proliferation of these cells. The low IgG production of B10 spleen cells during the secondary response to SRBC in vitro co uld be restored by IL-2 added to the medium. 50 U/ml of IL-2 increased the number of anti-SRBC IgG-producing cells 40 times in B10 cells, bu t only 4 times in A/J cells, so that the IgG production in B10 cells r eached the same level as that in the A/J cells without exogenous IL-2. We suppose that the limited IL-2 production in the low-responding str ain B10 is the cause of the low IgG responsiveness of these mice.