Effects of Cyclophosphamide Treatment on the in vitro Activity of Mouse Lymphoid Cells after Nonspecific and Specific Stimulation

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Abstract
A single injection of 300 mg cyclophosphamide (CY)/kg resulted in the mouse in a reduction of the numbers of lymphocytes. The minimal values for spleen and peripheral lymph nodes (PLN) were about 10% and were reached on day 3. The restoration of the spleen started on day 5, while the number of PLN cells was still low on day 21. CY treatment followed by immunization resulted in accelerated recovery and considerably enhanced cell numbers in both organs. Staining with fluorescent antisera revealed that, although the B cell is the main target cell of CY action, in the spleen the total percentage of B and T cells decreases during the period in which the total cell number increases. Immunization diminished the in vitro responsiveness of spleen and PLN cells on phytohemagglutinin (PHA) and concanavalin A (Con A), 7 and 11 days later. The response of PLN cells on lipopolysaccharide (LPS) was, however, strongly enhanced on day 7. CY pretreatment of normal and immunized mice yielded cell populations which behaved identically on nonspecific stimulation in vitro. Starting 5 days after CY, the PHA and Con A responses for spleen cells were impaired, while the initial low R values for PLN cells showed a steady increase. Stimulation of CY spleen cells with LPS resulted in R values of below 1. Specific in vitro stimulation of lymphocytes of immunized mice was performed with sheep red blood cells and a hapten-carrier complex. CY treatment before immunization resulted in an elimination of the in vitro activity on specific stimulation.