In vitro spleen cell proliferation following in vivo treatment with a synthetic glycolipid or lipid A in three mouse strains.

Synthetic glycolipid, maltose hexastearate (MHS), like LPS or lipid A is a B cell mitogen for outbred Swiss mice, inbred C3H/HeN and C3H/HeJ X C3H/HeN F1 hybrid but not for C3H/HeJ mice. MHS administered i.p. (10 micrograms) to Swiss, C3H/HeN, C3H/HeJ and C3H/HeJ X C3H/HeN F1 hybrid mice confers within 90 min an increased ability in the spleen cell populations such that they exhibit increased incorporation of 3H thymidine into cellular DNA in vitro. The spleen cells of MHS treated mice also respond in vitro more vigorously than controls to a T cell mitogen (Con A) but not at all differently from controls to a B cell mitogen (LPS). The stimulated cells are sensitive to anti theta serum + C' (experiment done with Swiss mice) and the Lyt 1,1 monoclonal antibody + C' (experiment done with C3H/HeN mice), indicating them functionally to be of T-helper variety. Unlike MHS, lipid A administration i.p. resulted in MHS like response in C3H/HeN but not in C3H/HeJ mice. MHS action has been traced to an induction of IL1 release by macrophages of MHS treated animals by chromatographic analysis of macrophage derived supernatants. IL1, in turn, according to the prevalent concepts would stimulate immature T cells to become mature IL2 producer cells, allowing T helper cell proliferation through IL2 release.