William M. Steven

The Relationship of Macrophages and Erythrocyte Receptors to Vascular Patterns in Vole Spleen

The spleens of two species of voles were studied to determine the relationship between arterial terminals, macrophages and antibody-mediated erythrocyte receptors. The vascular distribution was studied by vascular injections and by use of PAS-stained serial sections. Macrophages were identified by their positive metalophil and hydrolytic enzyme reactions and their ability to phagocytose carbon. Antibody-mediated erythrocyte receptors were localized and studied by using combined erythrocyte binding, and an acid phosphatase technique. White pulp capillaries and penicillate arteries branch from the central arteries. Some white pulp capillaries terminate in the reticular meshes of the marginal zones and some in funnel-shaped dilatations continuous with the marginal sinuses. These apertures and extensions of the perifollicular rings extend to the germinal centers. Penicillate arteries can be traced to the red pulp cords. Macrophages were found in the following locations: (1) between the coronary regions and marginal zones (marginal metalophils); (2) in germinal centers, (3) in marginal zones, and (4) in red pulp cords. Sheep erythrocytes bind over the macrophages of the germinal centers, over the marginal metalophils and over macrophages of the marginal zones. These bound erythrocytes lyse when incubated with complement. These results illustrate that there are marginal metalophils other than rats, and that erythrocytes binding over sections of spleen are associated with the white pulp macrophages. The germinal centers of vole spleen have several characteristics that are associated with white pulp compartments that are involved in generation of primary antibody responses.

Immunohistochemical comparison of T cell and macrophage population in mammary tissue of control and Trichinella spiralis infected rats

We have shown that antigen-specific T lymphocytes can mediate maternal-to-neonatal immunity during lactation. Present studies address the dynamics of lymphocyte accumulation in the mammary gland during normal and disease stimulated conditions. Monoclonal antibodies specific for total T cells, suppressor/cytotoxic and helper subsets, and macrophages were used in conjunction with immunohistochemistry to identify and count the individual cell types. In unstimulated mammary tissue, following a rise in T cells to maximal numbers in late pregnancy, the total number of T cells/high power field (HPF) was significantly diminished in early lactation and continued to decline to the late lactation period. Both the numbers of T cells/HPF located in the mammary alveolar epithelium and surrounding connective tissue were significantly reduced in early lactation as compared to late pregnancy. This indicates the possible passage of cells into the milk during lactation. Prior infection of the mother with Trichinella spiralis and a secondary challenge 48 h. before sacrifice caused a significant reduction in the number of T cells in the mammary tissue in early lactation as compared with unstimulated controls, indicating the possibility of an even greater outflow of T cells into milk. In controls, the T-suppressor/cytotoxic subtype showed a reduction in early lactation versus late pregnancy but showed no shifts in total cells/HPF during infection. The T-helper subtype in controls remained unchanged from late pregnancy to early lactation with a considerable decline in late lactation. However, the T-helper cells were significantly decreased in T. spiralis-treated animals as compared with noninfected controls in early lactation.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of Sheep Erythrocytes as Antigens in Rat Spleen

Although sheep erythrocytes (SRBCs) are extensively used as an antigen in immunological studies, their histological distribution in lymphoid tissues has received little attention. The objective of this study was to determine the histological distribution of injected SRBCs in rat spleen. SRBCs were labelled with fluorescein isothiocyanate (FITC) to facilitate their identification in spleen sections with fluorescence microscopy. Rats received intravenous injections of FITC-labelled SRBCs and were sacrificed at various periods after injection. At 15 min, SRBCs were distributed throughout the marginal zone and red pulp. After 4 h, intact SRBCs were located mainly in the red pulp, while the marginal zone contained fluorescent flocculent material. At later periods this material was present in the periarterial lymphatic sheath (PALS) and in the light and dark zones of the germinal centers. By 12 h, the most intensely labelled areas in the white pulp were the crescent-shaped light zones. In 12 and 24 h, the PALS contained numerous foci of labelled granules. Some of the dark zones also contained label. After 48 h, the only areas containing label were the light zones of the germinal centers.