Epithelioid granuloma formation requiring no T-cell function.

Muramyl dipeptide (MDP), a minimal structure in bacterial cell walls essential for their adjuvant activity, was incorporated in a water-in-oil emulsion and injected into the footpads of nude rats devoid of functional T cells. MDP thus injected evoked massive epithelioid granulomas in the draining lymph nodes, indicating that MDP induced epithelioid granuloma formation requires no T cells. This finding with other data available strongly suggest that epithelioid granulomas can be induced without immunologic reactions.