Immune response to Mycobacterium leprae: further studies on the assessment of humoral immune response in mice.

Immuncyte proliferation in the spleens of mice given both a primary and a second infection sixty days later, was detected soon after the second challenge was administered. Plaque-forming cell assay for both the direct and developed plaques indicated that all cells producing antibody of both immunoglobulin classes were present in the animals when they were administered the second challenge. Hemagglutinating antibody determinations indicated that IgG antibodies are recognizable at a time when the bacilli reach a stage of maximum multiplication in the mouse host. The IgM antibodies, however, become detectable within a short time after infection in animals given either a single infection or a dual infection, one fifteen days later and the other sixty days after the first infection. It is proposed that the low level of circulating antibodies and antibody-producing cells despite continuous, as well as enhanced, antigenic challenge could be due to the fact that in the mouse footpad M. leprae may be intrinsically less antigenic than organisms that cause systemic infection. Quantitative immunoglobulin assays tended to confirm the observations on the HA studies. Present studies have once again confirmed our previous observations viz that the number of plaques in the spleens of mice infected with M. leprae increases on secondary stimulation, whether it is administered within a very short time after the primary infection or given later in the course of infection. They have also indicated that an IgG response will occur in the infected animals at a time when the bacillary multiplication enters the logarithmic phase of growth of M. leprae, They have, however, not permitted the placement of the mouse model in the overall spectrum of human leprosy.