Mast cell and Mycobacterium leprae in experimental leprosy.

The association of mast cells and lepra bacilli was studied in the foot pad skin of immunosuppressed mice inoculated with 10(5) lepra bacilli. The mice were killed at intervals varying from 2 1/2-14 months postinoculation. M. leprae are found in large numbers in nerves, blood vessels, muscle fibres, hair follicles, sweat and sebaceous glands. Mastocytosis and extensive degranulation are seen at similar sites. Since these are the structures most affected in leprosy where the lepra bacilli and degranulating mast cells accumulate, there appears a close relationship between the two. This could be due to the composite role of mast cells in host tissue response and mastocytosis and degranulation may be related to this.