Proliferative activity of cells in mouse thymus and spleen under different diurnal regimens of interleukin-2 administration

Chronodependent effect of interleukin-2 on mouse spleen cells in the model of cyclophosphamide immunosuppression

We studied the chronodependent effect of IL-2 in the experimental model of immunodeficiency, cyclophosphamide-induced immunosuppression in mice. IL-2 in a dose of 100 U/ mouse was administered at 10.00 and 16.00 for 3 days after injection of cyclophosphamide. In contrast to the morning treatment with the cytokine, evening administration produced antiapoptotic effect on splenocytes and stimulated proliferation to a greater extent. This was accompanied by an increase in the number of CD4(+), CD25(+) and CD4(+)25(+) cells in the spleen to a level of intact mice. More pronounced effect of the evening mode of IL-2 administration on the proliferation and subpopulation composition of mouse spleen cells in the studied model can be associated with high blood level of CD25(+) cells at this time of the day.

Proliferative activity and subpopulation pattern of cells in murine thymus and spleen on the model of graft-versus-host chronic reaction under various diurnal regimens of IL-2 administration

We studied the effects of IL-2 administration at different times of day to female B6D2F1 mice with experimental immunopathology, graft-versus-host chronic reaction induced by the administration of lymphoid cells from parental female DBA/2 mice. Recombinant murine IL-2 was injected subcutaneously at 10.00 (group 1) or 16.00 (group 2) after the first cell transfer. Evening administration of IL-2 in contrast to its morning injection prevented cell proliferation in the thymus and spleen, decreased the number of apoptotic splenocytes, significantly stimulated differentiation processes in the thymus, increased the amount of CD4 (+) 25 (high) thymocytes, and decreased the number of CD4 (+) 27 (low) splenocytes. These findings can serve as a prerequisite for the development of chronotherapeutic schemes for immunocorrection.

An adoptive transfer method to detect low-dose radiation-induced bystander effects in vivo

The potential for irradiated cells to induce biological effects in their unirradiated neighbors (known as the bystander effect) has been observed repeatedly in vitro. However, whether bystander effects occur in vivo under the specific conditions relevant to low-dose radiation protection is still unclear. To test this, the fate of bystander cells in the mouse spleen was examined using an adoptive transfer method designed to replicate the rare, irradiated cells in an organ that might be expected after a low-dose-rate, low-LET radiation exposure. Splenic lymphocytes radiolabeled with low activities of (3)H-thymidine were introduced into the spleens of unirradiated recipient mice. In this study, the apoptotic and proliferative response of the neighboring bystander spleen cells was compared to the response of spleen cells in parallel control recipients that received sham-irradiated cells. Neither the local area surrounding lodged radiolabeled cells nor the spleen as a whole showed a change in apoptosis or proliferation either 1 or 3 days after adoptive transfer. Increasing the irradiated cell numbers, increasing the mean (3)H-thymidine activity per cell, or exposing cells ex vivo to an acute X-ray dose also had no effect. Possible reasons for the absence of a bystander effect in the spleen under these conditions are discussed.