Pteridines as a new marker to detect human T cells activated by allogeneic or modified self major histocompatibility complex (MHC) determinants.

Evidence is presented that activation of T cells by allogeneic or modified autologous cells leads to the specific production of two distinct molecular compounds of the PT class. One of these two PT has previously been identified as neopterin. The structure of the other is still under investigation. This conclusion was based on the following findings: a) In vitro both PT were produced by T cells proliferating in response to HLA incompatible allogeneic or to autologous EB-virus-transformed or TNP-haptenized cells. b) In vitro stimulation of T cells with mitogenic lectins or protein antigens, of macrophages with zymosan-complement, of B cells with PWM or EB-virus, and of NK effector cells with tumor targets failed to induce comparable release of these PT. c) In vivo increased amounts of both PT were excreted via the urine during allograft rejection and viral infections. It thus appears that the production of these PT is primarily a feature of activated T cells involved in the control of self integrity.