CELLULAR COMPOSITION OF CORYNEBACTERIUM-PSEUDOTUBERCULOSIS PYOGRANULOMAS IN SHEEP

The cellular composition of 46 pyogranulomas experimentally induced wi th Corynebacterium pseudotuberculosis in sheep was determined by immun ohistochemistry. Lesions localized in inoculation sites or draining ly mph nodes consisted of macrophage and lymphocyte layers distributed ar ound a necrotic center and surrounded by a fibrous capsule. In immatur e lesions, T cells of the CD4(+) subset predominated, whereas in matur e lesions proportions of CD8(+) T lymphocytes and cells expressing the gamma/delta chains for the T cell receptor increased. Numerous pyogra nuloma cells expressed the interleukin-2 receptor. In addition to thes e general characteristics, a large individual variability in the propo rtions of macrophage and T cell subsets was observed for lesions of th e same age, in particular for epithelioid macrophages. This heterogene ity suggests a different cellular pattern in relation to the persisten ce or the elimination of bacteria by the host.