SERUM LEVELS OF A NEGATIVE REGULATOR OF CELL-PROLIFERATION (ACSDKP) ARE INCREASED IN CERTAIN HUMAN HEMOPATHIES

One of the first known effects of the endogenous peptide N-acetyl-Ser- Asp-Lys-Pro (AcSDKP) is to inhibit entry into DNA synthesis of pluripo tent haematopoietic stem cells (CFU-S) in mice. A specific anti-AcSDKP polyclonal antibody allows the level of the tetrapeptide by to be det ermined by enzyme immunoassay with good sensitivity and specificity. W e present results demonstrating the presence of AcSDKP in humans: seru m levels of 34 healthy controls were found to be between 0.7 and 2.5 p m/ml, regardless of age and sex. High levels were found in 44% of asym ptomatic controls but only in 8% of AIDS patients out of a total of 37 patients with HIV. Subsequently, studies of serum levels were perform ed before treatment in 121 subjects with disorders of the non-lymphoid and the lymphoid lineages. Our results did not demonstrate any decrea se in serum levels, however a moderate or marked increase was noted in one-third of the subjects, which was greater in disorders of the non- lymphoid lineages (48% of 72 patients) than the lymphoid lineage (21% of 50 patients). The most significant differences were observed betwee n controls versus patients with myeloproliferative disorders (MPD, 24 patients: p < 0.001), controls versus patients with acute myelogenous leukaemia (AML, 15 patients: p < 0.02), as well as patients with AML v ersus patients with primary myelodysplastic syndromes (PMDS, 10 patien ts: p < 0.05). The pathophysiology of these abnormalities is discussed .