Immunohistological analysis of macrophages, B-cells, and T-cells in the mouse lung

Numerous studies have described the anatomy of the large lymphoid aggregates of bronchus-associated lymphoid tissue (BALT) in rabbits and rats. Less work has been performed on other immunocompetent areas of the respiratory tract, and available data again mostly describe rabbit or rat tissues. Little is known therefore of the microanatomy of the mouse lung immune system.

We report a study, devised in order to establish the immunohistological characteristics of normal healthy mice lungs, performed on whole lungs from 22 mice of various strains and/or ages. Snap frozen tissues were serially sectioned and analysed using histochemistry and immunohistological techniques. Scattered macrophages, IgA plasma cells, B and T cells were enumerated in each sample.

The largest population was that of macrophages. B-cells were numerous in all mice but 3 adults. T-cells were always present, L3T4+ often more numerous than Lyt2+ cells. Small lymphoid aggregates, composed of B or T cells (L3T4+ and Lyt2+) were seen in all mice, in the vicinity of a bronchiole and a vein. In 12/22 mice, a peculiarly elongated para-esophageal lymph node with large peripheral B-cell nodules and medullary T-cells was observed. In the five strains of mice studied, large variations were noted, affecting all the cell types studied, and related either to age or strain.

Besides providing a qualitative description and quantitative analysis of immunocompetent cells, this work reports age and strain-related variations in these cells' distribution. These data could be relevant for studies involving the analysis of mice respiratory immune responses to environmental antigens.