Immunologic aspects of leprosy as related to leucocytic isoantibodies and platelet aggregating factors.

The incidences of various iso- and autoantibodies in a random population of 112 unselected leprosy patients is presented. Low titers of leucocytic isoantibodies and platelet aggregating factor were detected in the sera of a variable number of such patients. The leucoisoagglutinins were found in 8% of the sera of tuberculoid as well as lepromatous leprosy patients, whereas the leucoisocytotoxins were detected in a larger percentage of the lepromatous (40%) as well as tuberculoid (28%) cases. The platelet aggregating factors (PAF) were positive in 51.2% and 45% of lepromatous and tuberculoid cases respectively. Of the 21 positive sera for PAF, the antiplatelet factor by antihuman globulin consumption test could be demonstrated only in 66.6% and 50% of lepromatous and tuberculoid sera respectively. To study the frequencies of these newly detected antibodies or antibody-like factor and to compare their occurrences with other well-documented autoantibodies present in the sera of leprosy patients: cryoglobulins, antinucleoprotein antibody and thyroglobulin autoprecipitin were also studied in the sera of the same population of leprosy patients. It has been observed that the simultaneous occurrence of all these auto- and isoantibodies in the serum of one patient is a rare phenomenon. Leucocytic and platelet counts of these patients having antibodies against leucocytes and platelets were found to be within normal limits. Accordingly, it is suggested that the low levels of antileucocyte antibody and antiplatelet factor are probably harmless to the hosts. On the other hand, it is postulated that these antibodies may act as enhancing factors by being specifically adsorbed on the lymphoid cells, thus rendering them unresponsive to mitogenic stimulus in vitro. From these studies it seems that leprosy, especially the lepromatous type, is associated with some of the serological features suggestive of an autoimmune aberration.