The in vitro colony assay was used to determine radiosensitivity and post-irradiation changes of guinea pig clonogenic bone marrow stromal fibroblasts (CFU-F). D0 of the CFU-F survival curve proved to be about 200 rad, while n is 1.4. Immediately after total-body exposure to 400 rad and to local exposure of tibias to 400 rad, the number of CFU-F diminishes in accordance with D0; it sharply increases after 6 hours and then decreases again. In the period between the eighth and twelfth day following local irradiation, the number of CFU-F doubled in the course of 30-35 hours but later the rate of recovery slowed down. Practically no CFU-F were traced during 3 months after local exposure to 2 krad.
The efficiency of cloning of stromal precursor cell in mouse bone marrow culture increases significantly (2-3-fold) in the presence of serum from mice immunized with type 5 group A streptococcus antigens (5-20 microl serum/ml culture medium) in comparison with intact animal serum. The levels of TNF-alpha and IFN-gamma are significantly reduced (2.7 times and more than 6-fold, respectively) in the sera of immunized mice in comparison with normal serum. Serum levels of IL-2, -4, -5, -10, and -12 were about the same in both groups; no granulocyte-macrophage CSF was detected. These data attest to appreciable effect of immunization with streptococcal antigens on the bone marrow stromal tissue; this effect is presumably mediated through serum cytokines.
The counts of stromal precursor cells in bone marrow transplants obtained from animals 2 months after their immunization with killed type 5 group A streptococcus vaccine drop almost 3-fold in comparison with transplants from normal donors. Six months after donor immunization, the count of stromal precursor cells in the transplants reaches the normal level. The count of stromal precursor cells in bone marrow transplants from normal mice transplanted to recipients 6 months after their immunization with killed streptococcus vaccine also virtually did not change in comparison with the counts in bone marrow transplants from normal donors transplanted to normal recipients. The weight and size of bone capsules of 6.5-month bone marrow transplants in intact recipients after transplantation from donors immunized 2 months before with killed type 5 group A streptococcus vaccine was 3-fold lower than in bone marrow transplants collected from intact donors. The content of stromal precursor cells in the femoral bone marrow of animals immunized with killed streptococcus vaccine was 2.5 time higher in comparison with the parameter in the femoral bone marrow of normal mice even 8 months after immunization. The results indicate a significant long-acting effect of streptococcal antigens on the bone marrow stromal tissue, specifically, on its osteogenesis potential.
Administration of S. typhimurium microbial mass to mice was followed by a significant increase (by 3-4 times) in the efficiency of cloning and number of stromal precursors in the femoral bone marrow. These parameters were maximum on days 1-3, but returned to normal by the 8th-15th day after immunization. As differentiated from intact animals, the expression of genes for proinflammatory cytokines IL-1β (day 1 after immunization), IL-6 (days 1-3), TNF-α (days 1, 3, and 6), and IFN-α (days 1-3) was detected in bone marrow cultures from immunized mice. The expression of genes for IFN-γ, IL-18, and IFN-α was decreased on days 1, 3, and 6 after immunization of animals, respectively. Gene expression for the anti-inflammatory cytokine IL-4 was observed on day 6 after immunization. Therefore, this system was not characterized by a decrease in the immune response of stromal cells. The stromal component of hemopoietic and lymphoid organs has the vector of influences in response to bacterial antigens. This vector is directed to the stimulation and progression, but not to the suppression of immune reactions. Our results indicate that resident stromal cells play a role in the immune response of the body.
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