Comparison of IgM, IgG and IgA responses to M.leprae specific antigens in leprosy.

Antibodies of IgM, IgG and IgA classes against M.leprae specific antigens (PGL-I, ND-O-BSA, and NT-O-BSA) were determined in the sera of 80 leprosy patients (28 untreated, 34 treated lepromatous and 18 tuberculoid), 25 tuberculosis patients and 33 normal individuals of Northern Thailand. No strong distinction in reactivity could be found between the three antigens. The IgM antibody assay yielded more positive results than assays for IgG and IgA. It was found that the positivity rates of IgM antibodies to all three antigens were highest in untreated lepromatous leprosy (82%). In tuberculoid leprosy, the positivity rates of IgM, IgG and IgA to the antigens were more variable, ranging from 22 to 50 percent. Patients with tuberculosis and normal individuals did not produce IgM antibodies against the antigens. The results suggested that the determination of IgM against the three antigens is a more sensitive and specific test for active leprosy than those of IgG and IgA. The relationship between the duration of treatment and IgM antibody levels in lepromatous leprosy (LL) was studied. Untreated LL patients had significantly higher IgM and IgA antibody levels than treated patients. There was no difference in IgG antibody levels between the two groups, and the levels of both groups were higher than normal controls. Serial determination of IgM antibodies in 7 LL patients revealed that treatment was strongly associated with progressive decrease in IgM antibody levels against all three antigens.

Agar plating technique for enumeration of IL-2 producing cells in human peripheral blood mononuclear leukocytes.

An agar plating technique for detection and enumeration of IL-2 producing cells from human peripheral blood mononuclear leukocytes (PBML) has been developed. This method is based on the principle that PHA-stimulated PBML, as effector cells, secrete interleukin 2 (IL-2) into soft agar containing mouse 3-day Con A blasts as IL-2 dependent responder cells. The IL-2 dependent Con A blasts proliferating around the IL-2 producing cells form colonies or clusters of cells and are easily visualized under a dissecting microscope. The development of IL-2 producing cells was optimum when 1 X 10(6) cells/ml PBML were stimulated with 2 micrograms/ml PHA-P for 4 hours, and when 2.5 X 10(5) cells were co-cultured with 6 X 10(6) Con A blasts in soft agar for 5 days. The average number of IL-2 producing cells in 10 normal healthy controls were 754 +/- 94 (mean +/- S.E.M.) cells/10(6) PBML. The numbers of IL-2 producing cells and the levels of IL-2 produced were highly correlated (r = 0.929). The subpopulation of lymphocytes in the colonies was shown to be mostly murine T-cells, since they were mostly Thy 1.2 positive, CD3 negative and surface immunoglobulin negative. This technique is very simple to perform and provides an accurate and straightforward means to enumerate IL-2 producing cells from human PBML in a variety of human immunologic disorders.

Enumeration of interleukin 2-producing cells from rat spleen.

A method for the enumeration of IL2-producing cells from rat spleen has been developed. Rat spleen cells were stimulated with concanavalin A (Con A), washed, then mixed with IL2-dependent cells (3 day Con A blasts) and plated in soft agar. Clusters of IL2-dependent cells formed around IL2-producing cells, giving colonies which were easy to count under a dissecting microscope. All experimental factors influencing development of colonies of IL2-producing cells surrounded by IL2-dependent cells were evaluated and set up. Optimum number of effector cells was 2.5 x 10(5) cells/culture, while optimum number of IL2-dependent cells was 6 x 10(6) cells/culture. Optimum concentration of Con A for IL2 stimulation was 40 micrograms/ml with an optimal stimulation time of 10 hours. Optimum incubation time for development of IL2-producing cell colonies was 5 days. The number of IL2-producing cells by this technique had a good correlation with the level of IL2 in the cell culture fluid (r = 0.885). When colonies were aspirated from agar and stained by Wright stain, a big purple stained cell at the center was surrounded by small cells in almost all colonies examined. All cells from colonies were fluoresed with anti-mouse Thy 1.2-fluorescein conjugate. However, they were negative with anti-mouse Ig-fluorescein conjugate. The number of IL2-producing cells was 816-2080 cells/10(6) of rat spleen cells with mean +/- S.E.M. = 1404 +/- 154/10(6) cells.