Macrophage colony stimulating factor (M-CSP) within cord blood sera may bepartially responsible for the reduced proliferation of cord blood T cells

We show that there are differences in the soluble factors in cord blood (CB ) and adult serum and that these differences play a role in T cell function . Thus? the mitogen and alloantigen-specific proliferative response of adul t T cells was enhanced with increasing concentrations of adult serum and CB serum, but to a lesser extent with CB serum. In addition, proliferation of T cells induced by stimulation through the T cell receptor alone (via CD3 stimulation), could be enhanced with adult but not CB serum. However, CB se rum enhanced the IL-2-specific proliferative response of pure T cells where as adult serum did not. To determine whether there was an anti-inflammatory cytokine within CB seru m which could induce these results, we assayed our serum samples for anti-i nflammatory cytokines. IL-13 could not be detected in any serum sample, whe reas IL-10 could be detected in adult but not CB serum (P < 0.002), However , there was a significant difference in the levels of macrophage colony sti mulating factor (M-CSF) detected in adult and CB serum samples (P < 0.01). M-CSF was detected in 6/7 CB serum samples (mean +/- SD was 3.8 +/- 2.3 ng/ ml) and 0/5 adult serum samples. Furthermore, anti-M-CSF antibody restored the reduced allo-response of T cells incubated in CB serum. Thus, M-CSF may act as a suppressor factor in CB serum. Whether this is suf ficient to explain the lack of an allo-response by the foetus to the mother , or the reduced graft-versus-host disease when CB is used instead of bone marrow in stem cell transplantation, is yet to be determined.