Effect of human serum from patients with haematological disorders on mouse pluripotent haemopoietic stem cells (CFU-S).

Sera from 25 individuals (9 healthy subjects, 6 patients with systemic lupus erythematosus, and 10 patients with a variety of haematological disorders) were tested for anti-CFU-S by incubating suspensions of mouse marrow cells with serum and then assaying the cell suspensions for their capacity to form spleen nodules in lethally irradiated mice. The sera from 2 patients (1 with a preleukaemic disorder and the other with a malignant 'histio'-lymphoproliferative neoplasm) had anti-CFU-S activity which behaved like antibodies, rather than like the non-specific cytotoxic activity found in various sera for heterologous tissues, which in the past has been attributed to 'natural antibodies' and which, in recent years, has, in some cases, been found to be related to activation of the alternative pathway of complement. The anti-mouse tissue activity in the sera of the 2 patients may be related either to cross-reactivities between certain mouse and human tissues or to cross-reactivities between exogenous agents such as bacteria and mouse tissues.