[ACTH of lymphocytic origin under normal and pathological conditions]

Evidence has accumulated that human peripheral blood mononuclear cells (PBMC) may release adrenocorticotropic hormone (ACTH) and endorphin-like peptides into the culture medium when stimulated with different substances such as Newcastle disease virus and the lipopolysaccharide of Escherichia coli. However, to our knowledge, no quantitative assessment of ACTH-LIR (like-immunoreactivity) in human PBMC has been reported. We thus utilized a radioimmunoassay for ACTH to find a median of 30 pg of ACTH-LIR in 10(7) PBMC of 11 normal subjects. ACTH-LIR was also detected in 7 different cell lines derived from patients with lymphoid and myeloid malignancies, two of them, JM and U937, showed values of 135 and 108 pg/10(7) cells respectively. Stimulation with IL-1 beta at the concentration of 1000 U/mL induced, after 48 h, a significant increase of intralymphocytic ACTH levels when compared to basal and 24 h values. The chromatographic characterization of this ACTH-LIR showed, at least, three molecular forms of immunoreactive ACTH; molecular weights were 31 kD POMC, 22 kD ACTH and 4.5 kD ACTH. We used northern blotting with human genomic DNA probe for POMC gene to evidence specific mRNA in PBMC; mRNA was also observed in a T lymphocyte cell line derived from a patient with lymphoma. We conclude that PBMC produce ACTH-LIR which may act as a paracrine immunomodulator similar to lymphokine and/or may signal the adrenal gland to secrete glucocorticoids.