Inhibition of Graft-vs .-host Reaction

When parental type lymphoid cells are injected into F1 hybrid animals there is usually a severe graft-vs .-host reaction (GVHR) . It has been shown that a proportion of animals will survive the acute episode, depending on the number of cells injected and the strain combination used, and that these animals are then tolerant to a second challenge by parental type cells (1) . We have previously shown that this tolerance could be transferred from GVH-recovered rats to normal rats by cross-circulation or parabiosis (2) . X or /0 irradiation of the transfused blood to doses of 1,000 rad did not inhibit the transfer of tolerance, indicating that serum factors were responsible for mediating this phenomenon . Initial attempts to transfer this tolerance by serum alone proved unsuccessful (2, 3), probably because insufficient amounts of serum were transferred. The following experiments were designed to elucidate the role of serum factors from rats undergoing or recovering from a GVHR using the relatively more sensitive technique of local GVHR (4) .