Graft-versus-Host Reactivity of Lymphoid Cells inhibited by Anti-recognition Structure Serum

F1 hybrid animals injected with parental strain lymphoid cells were reported to develop antibodies that specifically react with parental alloantigen receptors or "recognition structures" (RS)1,2. The effect of such "anti-recognition structure" (anti-RS) sera was demonstrated by blocking of the recognition event in vitro, using the PAR assay3. It seemed important to find out whether anti-RS sera were also active in vivo. For this purpose, inhibition by an anti-RS serum of the lethal graft-versus-host activity of parental lymphoid cells injected into newborn F1 hybrids was attempted.