Enzyme immunoassay of phagocytosis stimulating tetrapeptide "tuftsin" in normal and leprosy sera

The serum concentrations of the phagocytosis stimulating the tetrapeptide, tuftsin, were determined by competitive enzyme immunoassay in borderline tuberculoid/tuberculoid (BT/TT, 16 cases), borderline lepromatous/lepromatous (BL/LL, 16 cases), and in healthy controls (20 cases). Using checkerboard titration, 10 ng/well of diphtheria toxoid-p-aminophenylacetyl tuftsin (DTPT) conjugate when incubated with tuftsin antisera at 1:15,000 dilution with a preincubation time of 60 min with the competitor (tuftsin) followed by a further 60-min incubation onto the DTPT-coated wells gave consistent results with a sensitivity of 5 ng/well tuftsin. The mean serum tuftsin concentration was significantly lower in BL/LL patients (134.42 +/- 48.7 ng/ml, p less than 0.01) than in healthy controls (262.86 +/- 59.8 ng/ml), while BT/TT sera (210.94 +/- 75.5 ng/ml) showed slightly decreased levels than did normals, which was not statistically significant. The mean serum IgG levels in BL/LL and BT/TT patients (37.26 +/- 10.99 mg/ml; 28.08 +/- 6.57 mg/ml, respectively) showed significantly (p less than 0.001) higher concentrations than did healthy controls (12.3 +/- 3.6 mg/ml). These observations on the serum concentrations of tuftsin and IgG in leprosy individuals suggest that there is splenic dysfunction in BL/LL patients in terms of the processing of leukokinin to release the free, active molecule tuftsin.