Immunological dysfunctions in multiple sclerosis. I. Diminution of 'active' thymus-derived lymphocytes and presence of immunomodulating serum factors.

The peripheral blood of twenty-eight patients with multiple sclerosis (MS) was examined for 'active' thymus (TA) derived lymphocytes (PBL) and the presence of serum factors which impair the lymphocyte blastogenic response and the migration of leucocytes from capillary tubes. MS patients exhibited a significant reduction in the level of circulating TA lymphocytes (15.2+/-2.7 vs 22.9+/-2.9, P less than 0.001). Additionally, MS serum markedly impaired the mobility and the mitogen induced blastogenic response of autologous and allogenic (control) PBL. Impairment in the blastogenic response was observed only when serum was added at culture initiation or after 4 hr. The results support the concept of a generalized deficiency in the immune competence of MS patients. The pathophysiological role of a serum suppressive factor is discussed.