SILICOTIC LYMPH-NODE REACTIONS IN MICE - GENETIC-DIFFERENCES, CORRELATION WITH MACROPHAGE MARKERS, AND INDEPENDENCE FROM T-LYMPHOCYTES

Quartz was injected into a hind foot of BALB/c and DBA/2 mice and on d ays 40, 90, and 180 the progressive response ensuing in the draining p opliteal lymph node (PLN) was investigated by histopathology and immun ohistopathology. The area of silicotic nodules (ASN) was measured by m orphometry, and, by this parameter, strain BALB/c proved to be a high responder to quartz, and strain DBA/2 a low responder, albeit both str ains showed a similar degree of reactive lymphoid hyperplasia in the d raining PLN, Both strains also showed a similar quartz content in the draining PLN but in BALB/c mice quartz particles were concentrated in the ASN, whereas in DBA/2 mice they were evenly dispersed over the PLN . Because the silicotic response of athymic BALB/c nu/nu mice was even stronger than that of euthymic BALB/c mice, T cells are not required for the development of silicotic nodules, This fits the notion that qu artz is not an antigen and that high and low responder strains are MHC -identical, Because quartz-treated BALB/c, but not DBA/2 mice, showed a persistent expression of the macrophage differentiation markers MRP8 and MRP14, phenotypically the observed strain difference in silicotic responsiveness seems to be expressed at the level of macrophages.