Acute non-specific peritonitis was induced by injecting turpentine into rabbits' peritoneal cavity. The exudate cells were collected 1, 3, 8, and 14 days after the injection from 50 experimental and 10 normal rabbits. Normal peritoneal exudate consists of 87.1% small lymphocytes, 9.7% macrophages and small amount of polymorphonuclear granulocytes (PMG). One day after injection the number of PMG increased and fell to normal level 3 days after injection. The number of macrophages gradually increased and reached the peak value 14 days after injection and did not fall to the normal level 30 days after injection. Lymphocytes began to increase in number 8 days after injection and did not return to normal 14 days after injection. Histochemical studies showed that A1P of PMG exhibited strong positive reaction one day after injection and the reaction was weakened 3 days after injection; AcP of macrophages showed increasing activity 3 days after injection which reached maximum on the 5th day and began to decrease after the 8th day. PMG and macrophages were positive for fat staining. Macrophages showed maximal fat reaction 3 days after injection, but contained many vesicles negative to fat stain. Percentages of positively ANAE reactive T lymphocytes raised from 2% to 19.5% 5 days after injection. The above results show that during acute non-specific peritonitis induced by turpentine the changes of exudate cell components and histochemical activity may signify that they play a role in immunological function during inflammation.

A murine MTEC_1 thymus epithelial cell line established by us has been characterized. The cells were polyhydral and closely packed each other as epithelial like cells. Using anti-keratin antibody, the keratin were shown in cytoplasm of all cells. Under electronmicroscope, bunches of tonofilaments were clearly shown in the cytoplasm, and desmosomes were seen between neighbouring cells. Using anti-mouse epithelial cell monoclonal antibodies for immunohistochemical study, nearly all of the MTEC_1 cells were MTS33 positive. It suggests that MTEC, cells were derived from the epithelial cells located in medulla. The majority of the MTEC_1 cells have normal mouse diploid chomosome number of 40. These results provide evidence that MTEC, cell line is normal murine thymus epithelial cells.

Fresh cryostat sections from the thymus of BALB/c adult mice were processed with semipermeable membrane technique for demonstration of non-specific esterase (NE). The various cell types and the pattern of their distribution may be showed, because this technique may preserve the total enzyme activity of cells. The NE activity of epithelial reticular cells (ERC), thymic nurse cells (TNC), and interdigitating cells (IDC) are lower, but macrophages (M?) show a high activity. Cortical ERCs appear as a sponge-like network. Medullary ERCs may be divided into two cell types, i. e. low and high activity cells. The distribution of the latter shows foci-like pattern. M? present in both the cortex and medulla, in the cortico-medullary border they are prominent and may form rosettes-like structure with thymocytes. The thymus was also studied with immunohistochemical method using the monoclonal antibody of rat-anti-mouse thymic stromal ceils (MTS-6). This observation enable studies on the type of thymic stromal cells formed thymic microenvironment under LM.

The ultrastructural localization of acid phosphatase in the cells of mouse thymic cortex was described by using Robinson and Karnovsky method with cerium chloride as capture agent. The results indicated that the enzyme activity was localized mainly on the plasma membrane of epithelial reticular cells and thymocytes, especially where both of them were in contact with each other. Acid phosphatase activity was also found in the invaginations of plasma membrane, the vesicles near the plasma membrane, the saccules of the Golgi zone, the lysosomes, and a part of the vacuoles of epitheleial reticular cells. The lysosomes and the dense granules of cytoplasm, as well as on the some area of plasma membrane of the macrophages showed the enzyme activity. The enzyme activity was demonstrated in the cytoplasm and on the plasma membrane of degenerated thymocytes. The role of acid phosphatase in thymic cortex cells was discussed.

The thymic cortex is the important site for thymocyte differentiation, maturation and selection. Direct cell-cell interactions between thymocytes and distinct stromal cells are an important pattern to demonstrate the essential role in T-cell development. In order to approach the mechanism of their interactions, ultrastructural cytochemical localization of 5'-nucleotidase activity in the thymic cortex of BALB/c mice were investigated by means of Robinson and Karnovsky method using 5'-AMP or 5'-IMP as the substrate, cerium as the capture agent, and levamisol (an inhibitor of nonspecific alkaline phosphatase) was also used. The cytochemical distribution of the reaction products from both the 5'-AMPase and 5'-IMPase activity was essentially similar. The enzyme activity was localized on the extracellular side of the plasma membrane of the epithelial reticular cells and some thymocytes, especially on their contact faces with each other. 5'-nucleotidase activity was also found in the lysosomes of macrophages and in the vacuoles, and vesicles near the plasma membrane and some lysosomes of epithelial reticular cells. The biological significance of the 5'-nucleotidase in thymic cortex was discussed.