Molecular basis of familial and acquired phagocytosis deficiency involving the tetrapeptide, thr-lys-pro-arg, tuftsin.

The biological activity and metabolism of the phagocytosis stimulating tetrapeptide (Thr-Lys-Pro-Arg) tuftsin, are discussed. Its effect is shown to be highly specific. It stimulates the phagocytic activity of the blood polymorphonuclear leukocyte. A unique familial deficiency of the tetrapeptide is described. In such patients, moderate to severe infections occur at high frequency. These are most pronounced in children. Biochemical and symptomatic evidence can readily be obtained in one or more children. At least one parent of either sex shows clinical signs or laboratory evidence of defective phagocytosis. Another type of deficiency results from removal of the spleen or from loss of specific function due to leukemic infiltration or embolism.