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Priming in recipient mice unable to generate a primary antibody response: kinetics of priming for an IgM response.


 The enhanced production of direct plaque-forming cells (DPFC) to a second dose of sheep erythrocytes (Srbc) has been demonstrated in irradiated mice restored with a limiting number of unprimed spleen cells. The limiting number of spleen cells was such that only a proportion of the recipients could respond to a primary dose of Srbc given at the time of spleen cell transfer. The most important finding was that 100% of such mice could respond to a second dose of Srbc given 1 week after cell transfer and the magnitude of the response was 18- to 36-fold greater than that of similar mice receiving only the first dose of antigen. The development of enhanced DPFC responsiveness was shown to require the initial dose of antigen and both its induction and elicitation were antigen-specific. Since enhanced responsiveness occurred in a population of mice not all of which could make a primary DPFC response, these results have been interpreted to indicate that priming occurs in a cell population not directly involved in initiating the primary antibody response.