Release of soluble factors from lymph nodes containing mycobacterial granulomas and their effect on fibroblast function in vitro

Macrophage heterogeneity in tissues: phenotypic diversity and functions

During development and throughout adult life, macrophages derived from hematopoietic progenitors are seeded throughout the body, initially in the absence of inflammatory and infectious stimuli as tissue-resident cells, with enhanced recruitment, activation, and local proliferation following injury and pathologic insults. We have learned a great deal about macrophage properties ex vivo and in cell culture, but their phenotypic heterogeneity within different tissue microenvironments remains poorly characterized, although it contributes significantly to maintaining local and systemic homeostasis, pathogenesis, and possible treatment. In this review, we summarize the nature, functions, and interactions of tissue macrophage populations within their microenvironment and suggest questions for further investigation.

Interleukin 1 and prostaglandin production by cells of the mononuclear phagocyte system isolated from mycobacterial granulomas

A study has been made of the activity of interleukin 1 (IL-1) and prostaglandins (PGs) in the culture supernatants from unstimulated and lipopolysaccharide (LPS)-stimulated mycobacteria-induced granuloma cells. Both epithelioid cells from bacillus Calmette-Guerin (BCG)-induced granulomas and macrophages from Mycobacterium leprae-induced granulomas, separated on a fluorescence-activated cell sorter using monoclonal antibody specific to guinea pig macrophages, spontaneously secreted low levels of IL-1 (assayed by thymocyte comitogenic and fibroblast mitogenic activities) into culture supernatants. However, culture supernatants from LPS-stimulated epithelioid cells showed significantly higher IL-1 activity than those from unstimulated cells. In contrast, LPS stimulation of M. leprae granuloma macrophages failed to enhance IL-1 production. Nevertheless, IL-1 activity in the culture supernatants from stimulated mycobacterial granuloma cells of both types was much lower than that from LPS-stimulated peritoneal exudate macrophage culture supernatants. There was no detectable amount of prostaglandin E2 (PGE2) in the culture supernatants from both unstimulated and LPS-stimulated BCG- and M. leprae-induced granuloma cells in comparison to much higher levels of PGE2 produced by unstimulated (0.28-6.2 ng/ml) or LPS-stimulated (greater than 15 ng/ml) peritoneal exudate macrophages. However, BCG granuloma cells either secreted prostaglandin F2 alpha (PGF2 alpha) spontaneously or produced comparable levels of PGF2 alpha to those from peritoneal exudate macrophages on stimulation, while M. leprae granuloma macrophages produced much lower levels of PGF2 alpha.

The mononuclear phagocyte system in granulomas

A comparison is made between immunologically induced and non-immunologically induced granulomas in guinea-pigs injected with metals (zirconium and aluminum) or with mycobacteria (BCG vaccine and Mycobacterium leprae). Immunological granulomas were characterized by epithelioid cells and fibrosis, whereas non-immunological granulomas contained phagocytosing macrophages with little evidence of fibroblast activation. Epithelioid cells carry the same specific macrophage antigen as phagocytosing macrophages and this can be detected by the use of a specific monoclonal antibody. However, they differ from phagocytosing macrophages in that they are poorly phagocytic, not glass adherent and lack Ia antigen. They are however secretory cells with rough endoplasmic reticulum. A relation between the presence of these cells and increased collagen synthesis is indicated. A study of accessory cell function showed that the epithelioid cells of BCG granulomas were able to support mitogen-induced but not antigen-induced proliferation of T lymphocytes. The macrophages of M. leprae granulomas did not support either a mitogen- or antigen-induced proliferative response.