Expression of interleukin-1 beta, interleukin-6 and tumour necrosis factor alpha by macrophages in canine lymph nodes with mineral-associated lymphadenopathy, granulomatous lymphadenitis or reactive hyperplasia.

The distribution of CD3+ T lymphocytes and the expression of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF alpha) by macrophages in canine lymph nodes with mineral-associated lymph-adenopathy, granulomatous lymphadenitis or reactive hyperplasia was examined immunohistochemically. In areas of preserved lymph node architecture, CD3+ T lymphocytes were located in the paracortex, with scattered cells in the follicular mantle and germinal centre, and small aggregates in the medullary cords. T cells were prominent within areas of diffuse granulomatous inflammation and formed a peripheral rim around microgranulomas. TNF alpha expression was demonstrated in macrophages from seven of 11 dogs with mineral-associated lymphadenopathy, one of five dogs with granulomatous lymphadenitis and three of five with reactive hyperplasia. Positive macrophage staining for IL-1 beta and IL-6 was seen in two lymph nodes with reactive hyperplasia. Lymph nodes from control (clinically normal) dogs showed no evidence of cytokine expression. Neutrophils expressing IL-1 beta were observed within the medullary sinuses of two lymph nodes with mineral-associated lymphadenopathy and one with reactive hyperplasia, and in the inflammatory infiltrate in one lymph node with granulomatous lymph-adenitis. The sensitivity of immunohistochemical examination as a means of detecting cytokines in abnormal tissue is discussed.