Detection of properdin mRNA in human peripheral blood monocytes and spleen.

Properdin serves a critical role in the alternative pathway of complement by stabilizing the C3bBb complex. Early studies to determine the properdin sequence relied on amino acid sequencing of enzymatically cleaved properdin and only yielded partial sequence data. Recently Nolan et al. reported a properdin mRNA sequence obtained from the U937 myelomonocytic cell line. We sought to detect properdin mRNA in two normal human tissues and to compare those sequences with that obtained from the U937 cell line. Cytoplasmic RNA harvested from human spleen and peripheral blood monocytes served as a template for first strand synthesis. The cDNA was then used as a template for polymerase chain reaction. A properdin message was detected in both spleen and peripheral blood monocytes but not in peripheral blood neutrophils. The sequence was nearly identical to that obtained from the U937 cell line. These experiments demonstrate that peripheral blood may be used as a ready source for properdin mRNA and will faster studies to define the defect in properdin-deficient patients.