Abstract. The potential clinical applications of GnRH agonists are growing. We studied the effects of two GnRH agonists on the adult female rat thymus in 4 experiments. GnRH agonists administered sc and continuously significantly increased wet and dry thymic weights (absolute and relative). Thymic enlargement was related to the duration of treatment with GnRH agonists. The maximum increase in thymic weight occurred at approximately 18 days following initiation of treatment with GnRH agonists. Thymic enlargement does not appear to involve enhanced mitotic activity as measured by incorporation of tritiated thymidine into thymic tissue and thymic DNA. Histologic examination and computer-assisted morphometric analysis of thymuses indicated an increase in cortex to medulla ratio most pronounced at 10 and 18 days of GnRH agonist treatment. No consistent increases in splenic weight or bone marrow cell counts were observed. Thymosin alpha-1 but not thymosin beta-4 increased in GnRH agonist-treated rats. Thymic weight correlated negatively with ovarian and uterine weights, relative adrenal weight, serum estradiol, LH, and positively with thymosin alpha-1. Exogenous estrogen administration reversed GnRH agonist-induced thymic weight increase. Whether GnRH agonists have direct thymic effects remains to be determined.

SUMMARYAfter immunization with Sindbis virus, T-cell deficient nude mice, compared to normal littermates, were equally protected against challenge with Sindbis virus. However, the nude mice showed about one-tenth the protection observed with normal littermates after challenge with Semliki Forest virus at a dose of too LDs0. This is consistent with our previous interpretation that sensitized T-cell populations play a major role in cross protection between the two togaviruses. The remaining low level of specific cross protection in nude mice (detectable only at a challenge dose of IO LDs0 ) could not be attributed to an anamnestic response of neutralizing antibody to the challenge virus or to an effective antibody-dependent, complement-mediated cytolysis of infected cells in vivo. Other possible compensatory mechanisms to explain the low level of specific cross protection in nude mice are discussed.

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The use of granulocyte transfusions in profoundly neutropenic patients has increased markedly in recent years. Whenever a pulmonary infiltrate develops during the course of these transfusions, the question arises as to what role the transfusions are playing and whether the transfusions should be discontinued to prevent pulmonary deterioration. We have analyzed our recent experience of 593 granulocyte transfusions in 93 patients. 18 patients (19%) developed respiratory compromise or pulmonary infiltrates at some time during the course of granulocyte transfusion. 6 of the 18 cases were reactions to the granulocytes while the remainder were due to fluid overload or other causes. The risk of pulmonary complications did not correlate with the development of cytotoxic leukocyte antibodies, length of transfusion, or concomitant use of Amphotericin. They appeared to be more common in patients with active sepsis. Acute life-threatening pulmonary reactions were rare. Patients receiving granulocyte transfusions should be monitored carefully for pulmonary infiltrates, but other cases should be sought before the transfusions are discontinued.