Experimental modulation of the reactivity of pleural milky spots (Kampmeier's foci) by Freund's adjuvants, betamethasone and mycobacterial infection

Abstract

We studied the response of milky spots in the parietal pleura of the rat and mouse to intrapleural instillation of immunomodulatory agents such as complete or incomplete Freund's adjuvants and betamethasone, and also to infection by mycobacteria (M. avium). Both incomplete (mineral oil) and complete (mineral oil plus dead mycobacteria) adjuvants, as well as M. avium infection, induced a striking increase in the size and cellularity of the pleural milky spots whereas betamethasone caused a slight atrophy. The extensive inflammatory infiltrates observed after adjuvant injection differed between milky spots reactive to complete and incomplete Freund's adjuvants. Fifteen days after adjuvant administration, the pleural milky spots of rats were still enlarged and hypercellular but differences were noted in the size of milky spots of the pleura between the 2 adjuvant treatments: animals submitted to injection of complete Freund's adjuvant showed an increase in the size of milky spots from d 3 to d 15, while the size of milky spots of the incomplete Freund's adjuvant treated group showed a decrease in size from d 3 to d 15. The milky spots at d 15 were well organised: reticulin fibres permeated the whole area of the milky spot and the different cell types were evenly distributed. Histiocytes, which were previously confined to the inner layer, were now the main cell type in all areas of milky spots. A moderate number of mast cells and a few eosinophils were also seen. Complete Freund's adjuvant caused the formation of granulomas in the milky spots, a change that was not detected in animals treated with incomplete adjuvant.(ABSTRACT TRUNCATED AT 250 WORDS)