The eosinophilic leukocyte. Fine structure studies of changes in the uterus during the estrous cycle

A light microscopical study of healing incised dermal wounds in rats, with special reference to eosinophil leucocytes and to the collagenous fibres of the periwound areas

Incised wounding of rat skin had a significant effect on the number of eosinophils both within the scar and in the adjacent areas. The numbers increased, after the inflammatory phase, to a peak between the 7th and 12th-14th days after wounding and remained elevated for the rest of the 30-day experimental period. In the areas contiguous to wounds, the dense bundles of collagenous fibres characteristic of normal dermis became progressively more dispersed from the 3rd to the 14th day, and then gradually re-aggregated into bundles. The fact that eosinophils, which are known to be collagenolytic, increase in numbers and change in morphology at the same time as newly formed scar collagen is remodelled and fibres around wounds are aggregated indicates a role for these cells in connective tissue metabolism. It is suggested that the dispersion of the collagenous fibres in the areas around wounds which occurs before the rise in eosinophil numbers could be related to the known increase in sulphated glycosaminoglycans around incised wounds.

Cellular mechanisms involved in cyclic stroma renewal of the uterus. III. Cells of the immune response

The principal cell types associated with the humoral immune response (monocyte-macrophages, lymphocytes, and plasma cells) are numerous in the endometrial stroma of the uterus during the first four postpartum days in two types of mammals, the marsupial North America opossum and the eutherian albino rat. This transietn cellular differentiation coincides with the physiologic period of rapid uterine regression which includes massive reduction in the amount of extracellular stromal material. In addition, heterophils and eosinophils, cell types also known to be associated with phagocytic and immunologic activity, appear in the stroma during the first two postpartum days; their presence may, however, be associated more directly with the postpartum estrus that occurs on day 1 postpartum than with endometrial regression. Thus, the five cell types, which are known in pathologic conditions to be components present in the inflammatory response to a foreign antigen, are conspicuously present in the normal regressing endometrium. Furthermore, there is ample ultrastructural evidence of frequent macrophagic-lymphocytic interaction, transformation of lymphocytes, and active secretion by plasma cells during this early postpartum period. An hypothesis has been derived by uniting this new description of endometrial stromal cell differentiation with the existing literature on uterine collagenase activity, an important feature of postpartum regression (reviews of Gross, '74; Harris and Krane, '74). It is based on the assumption that during regression the extracellular action of neutral collagenase (and possibly other extracellular proteases) release new antigenic sites in proteins located in the ground substance. In the case of collagenase, these transient antigenic sites would arise at the locus of enzymic cleavage as well as from the subsequent denaturation of the fragments of the collagen molecule. This endogenous antigenic stimulus would be strong and temporary, and would lead to the cellular manifestations of the transient humoral immunologic response which are evident in the regressing stroma of these two mammals. This humoral immune reaction may be one of the regulatory mechanisms involved in the cyclic renewal of the extracellular compartment of the uterine stroma.

Pseudoeosinophilic leucocyte response to denuding the rabbit cornea

After scraping the epithelium from the rabbit's cornea, pseudoeosinophilic leucocytes appeared in the limbic area within one hour and began to advance, presumably by means of pseudopodia, into the anterior corneal stroma. The cytoplasmic granules of these cells were intensely stained by eosin and by the Undritz peroxidase method during the first hour, but were not stained by the PAS method until the eighteenth hour. Electron microscopy failed to show crystalloids in the granules. The cellular changes were followed until the fourth day, by which time most of the cells had disappeared by fragmentation, karyorrhexis and lysis.