INCREASED PROLIFERATIVE ACTIVITY, LOSS OF BETA-ADRENERGIC-RECEPTOR FUNCTION AND CLASS-I MAJOR HISTOCOMPATIBILITY COMPLEX ANTIGEN SURFACE EXPRESSION IN A MODIFIED LYMPHOMA CELL-LINE

The molecular interaction of class I major histocompatibility complex (MHC) antigens (Ag) and of beta-adrenergic receptors was previously de monstrated on lymphocytes. By long-term culturing with high concentrat ion of foetal calf serum, the murine S-49 lymphoma cell line was modif ied (S(49)m) giving phenotypic alterations in beta-adrenergic receptor s and class I Ag expression. S(49)m cells displayed a reduced number o f beta-adrenergic sites that were uncoupled to the adenylate cyclase s ystem. These were unable to respond to beta agonist stimulation, despi te the fact that direct activation of Gs could be achieved with alumin ium tetrafluoride. Although S(49)m cells showed normal expression of t he thy 1.2 Ag, they displayed no expression of class I Ag of the d hap lotype. This was assessed by the evident lack of cytotoxic activity of specific monoclonal antibodies (Mo Ab) and of their binding. When per forming IFI staining on permeabilized cells, we found positive stainin g with anti-class d Ab inside the cell. This loss of expression and ac tivity of beta-adrenoceptors and the internalization of class I Ag wer e accompanied by a higher rate of proliferation in S(49)m cells. The p ossibility that the loss of both molecules would modify the biology of the cell is also discussed.