Changes in the Expression of Immune Proteasomes in the Liver after the Induction of Portal Tolerance Depending on Donor-Recipient Differences in Rats

Induction of donor-specific tolerance in outbred Wistar rats (RT1^u) and inbred August rats (RT1^c) increased the expression of immune proteasome subunits in liver with a peak on day 7 after beginning of the induction. The increase in the level of immune subunits LMP2 and LMP7 was more pronounced in the liver of August rats in comparison with Wistar rats (by 2 and 6 times, respectively), which was associated with higher concentrations of monoamines in the CNS of August rats. After induction of donor-specific tolerance in August and Wistar rats, the immune subunits were in cells of sinusoidal lining and in cells located in sinusoid lumens. It can be suggested that immune proteasomes in these cells producing antigenic peptides for presentation to immunocompetent participate in the suppression of their activity and form the molecular basis for the development of donor-specific tolerance at very early stages of this process.

[Proteasomes on thyroid tissue allotransplantation under induction of donor specific tolerance in rats]

The proteasomes in the liver of August rats (RT1C) were investigated 30 days after the allotransplantation of Wistar rat (RT1u) thyroid tissue under renal capsule with/without induction of donor specific tolerance by donor splenocyte intraportal administration. The level of the total proteasome pool, immune proteasomes containing the LMP2 and/or LMP7 subunits, proteasome 19S- and 11S-regulators was defined. The intact and sham-operated August rats were used as control groups. The level of all immune proteasome forms and 11S regulator increased while the level of the total proteasome pool and 19S regulator decreased in the liver of experimental animals compared to the control groups that indicated changes of liver functional state after transplantation. The 19S/11S ratio increased in the liver of non-tolerated rats compared to tolerated animals. In the liver of tolerated rats with survived transplants, the quantity of mononuclear cells, expressing the immune subunit LMP2, greatly increased in comparison with control and non-tolerated animals. Study of the survived transplants showed the increase of the ratio of LMP2/LMP7 immune subunits and 19S/11S regulators in them compared to the tissue replacing the rejected transplants. In the control intact thyroid tissue, the immune proteasomes were almost not revealed, while 19S/11S ratio was maximal. Thus, the development of the immune reaction or its suppression is accompanied by change of the balance between different proteasome forms. The immune subunit LMP7 and 11S regulator are connected with the response against donor tissue. On the contrary, the immune subunit LMP2 and 19S regulator are likely to be important for the immune tolerance development and survived tissue functioning. The low content of the immune proteasomes in the follicle cells was found by immunofluorescence assay. The formation of antigens for major histocompatibility complex class I molecules was impaired by low immune proteasome content that led to immunological tolerance to hormone-producing follicle cells.