[Use of the macrophage migration inhibition test in the study of relationships between mycobacterial antigens]

In this study, 3 groups of 15 rabbits each were sensitized with killed Mycobacterium tuberculosis, M. kansasii or M. avium bacteria. The sensitization was performed through the footpad. Eighteen days after sensitization, cellular immunity of the rabbits was tested with total homologous and heterologous antigens by direct and indirect migration inhibition tests using spleen macrophages. The bacteria were sonicated and centrifuged at 100,000 g for 1 h. The supernatant was used as the cytoplasmic antigen. Assayed by indirect migration, the migration index (MI) for homologous antigens was highly specific compared to heterologous antigens (MI of 0,60-0,65 compared to 0,79-0,96). The patterns obtained for rabbits sensitized with M. tuberculosis or M. kansasii when assayed by direct migration in the presence of homologous antigens (MI of 0,58 and 0,61, respectively) were similar. M. avium gave a distinct pattern. The results obtained indicate that crossed activity with heterologous antigens would be due to the presence of common components in the total antigens of the mycobacteria in question. On the other hand, the lower specificity of the direct test would result from the role played by humoral factors and antibodies, which might influence simultaneously migration of the target macrophages.