During complex research using anatomical, histological, morphometric, histochemical, lectinhistochemical and statistical methods regularities of morphogenesis of menisci of rat knee joint in the postnatal period after intrafetal injection of antigens were studied. For the first time it was established that in rats after intrafetal injection of antigens a decrease in the linear dimensions of the menisci was observed. After the birth the menisci of animals of the experimental group have more curved femoral surface due to thickening of the outer parts and thinning of the internal parts, which is a manifestation of dysplastic changes in the menisci. It is shown that after the prenatal action of antigens there are changes in the rates and terms of the morphogenesis of the menisci of the rat knee joint which is manifested by their thickening during the 1st and 3rd weeks of postnatal life and thinning during the 2nd and 3rd months, which breaks the congruence of articular surfaces and can become the basis for the development of diseases of the musculoskeletal system. At the same time, changes in the rates and terms of the formation of the pelvic limb were observed in animals after intrafetal injection of antigens which is manifested by the decrease in their linear dimensions during the first five days and the increase from the 11th till the 60th day. In the menisci of rats after prenatal injection of antigens from the birth till the 60th day of life an imbalance in the ratio of the cells and extracellular matrix is observed. In the menisci of intact animals lymphocytes are found only in the outer zone. It was established that in the menisci of antigen-influenced animals there is the increase in the total number of lymphocytes and PNA+-lymphocytes in the outer zone, which persists until the 11th day. The "fibroblast-like cell / lymphocyte" ratio is changed, which is accompanied by the sharp increase in the number of fibroblast-like cells with the faster subsequent decrease up to the 60th day of life. In the connective tissue of the menisci of rats after intrafetal injection of antigens the increase in the synthesis and accumulation of hyaluronic acid, chondroitin and a decrease in the content of low-sulfated glycosaminoglycans are observed during the first three weeks of life, which affects the cushioning properties of the meniscus tissue during the formation of motor activity in animals. In the menisci of experimental rats the increase in the number of immature collagen fibers in both zones during the 1st week after birth and their total content during the 2nd month in the inner zone and the decrease in the number of collagen fibers in the experimental group in the outer zone compared to the control during the first two months were found. On this background in the menisci of rats after intrafetal injection of antigens there is the increase in elastic fibers amount during the first two weeks of postnatal life and their decrease more intensive during the 2nd month, which affects the elasticity and stiffness of the meniscus. The data obtained on the distribution of receptors to the panel of lectins and their content in the matrix of the inner and outer zones of the meniscus against intrafetal injection of the antigens indicate a change in the dynamics of the content of carbohydrate residues and, as a consequence, the effect of the altered microenvironment on the maturation processes of tissue structures. The basis of the changes that were noted is the premature exit of immunologically immature PNA+-lymphocytes from the thymus of fetus into the organs against the background of prenatal antigenic exposure, as well as the change in the ratio between them and the surrounding cells of connective tissue. This leads to the influence on the processes of proliferation, differentiation and maturation of the cells of the connective tissue of the pelvic limb in newborns, as well as their synthetic activity, and, as a result, further irregularities in the rates and terms of the morphogenesis of separate structures, in particular the meniscus. During the 1st and 3rd weeks, when changes occur in the specificity of the motor activity, the cartilage tissue of the meniscus reacts excessively to the mechanical stimulus, which leads to an increase in its thickness. Subsequently, immature tissue cannot perform its function fully, which leads to a thinning of the meniscus. In the future, this can be the basis for the development of diseases of the musculoskeletal system.
