The article demonstrates that in children with thymomegalia the process of T-lymphopoesis in thymus is depressed. The functional condition of thymus was evaluated by detection of T-receptor excisional rings using polymerase chain reaction technique in real time. The T-receptor excisional rings are circular molecular structures developing in the process of rearrangement of V-genes of T-cell receptor. The most intensive and statistically reliable decreasing of content of T-receptor excisional rings in lymphocytes of blood is detected during first two years of life: 29.6 (18.1-41.0) copies per 1000 lymphocytes against 73.3 (54.0-83.8) copies in control. Hereinafter, (after two years) difference in level of T-receptor excisional rings inc children with thymomegalia in comparison with children without enlargement of thymus is less expressed i.e. it amounts to 1.8 times at the age before 10 years. In individuals of older age thymomegalia is a rather rare pathology. The examination of single patient aged of 40 years and with thymomegalia factually total absence of T-receptor excisional rings in cells of his blood was established.

The children of early age with thymomegalia and acute obstructive bronchitis suffer from lower T-lymphopoiesis in thymus gland evaluated on content of T-receptor excision rings. The T-receptor excision rings represent ring-shaped DNA molecules detecting only in T-cells recently emigrated from thymus gland. They serve as a measure of intensity of maturation of T-lymphocytes and their migration from this gland i.e. functional activity of this organ. The addition of immune modulating preparation tactivin to the complex treatment of acute obstructive bronchitis promotes repairing of affected T-lymphopoiesis. Besides, content of T-receptor excision rings practically reaches the level detected in children without thymomegalia.

The T-cell receptor excision circles (TREC) content in peripheral blood lymphocytes is considerably decreased in patients with autoimmune rheumatoid arthritis. TREC are circles which are excised from the genomic DNA in the thymus during rearrangement of TCR genes. High TREC level is peculiar to T-cells which have recently emigrated from the thymus (Recent thymic emigrants RTE). The degree of TREC-contaning lymphocytes decrease with age is significantly higher in patients with rheumatoid arthritis in comparison with age-matched healthy donors. So we can state premature thymus aging in this autoimmune disease. Expressiveness of distinctions of the TREC content (in comparison with TREC level in healthy donors) is increased with age: it 2-fold for age of 41-50 years, almost 4-fold for age of 51-60 years, 45-fold for persons older than 60 years. The obtained data testifies that thymic T-lymphopoiesis is reduced in autoimmune processes; at the same time intensive proliferation of peripheral T-cells and RTE redistribution in the organism with rapid migration to the tissue damaged by autoimmune process may also contribute to TREC level decrease.