抗体クラススィッチ過程の活性化自由エネルギー

Abstract

Membrane-bound form IgM (IgM_m) and total IgM (IgM_t) transcriptions were measured by real time PCR method in the thymus and the spleen of BALB/c male mice and the change of logIgMmagMt ratios with age were detected. Kinetics was applied and both the rate constant k_1, corresponding to the process in which IgM_mtranscribing cells differentiate into ones transcribing secretory type IgM and k_2, corresponding to the process in which those into cells transcribing other class Ig, were determined. ΔG_1^* and ΔG_2^*, free energy of activation corresponding to k_1 and k_2 process in each, were calculated from k_1 and k_2 by application of theory of absolute reaction rate. ΔG_1^* and ΔG_2^* were 110 to 120 kJ/mol both in the thymus and in the spleen. By considering the phenomenal differences in k_1 and k_2 processes, the difference of ΔG_2^* and ΔG_1^* might be able to regard as the free energy of immunoglobulin class switch process ΔG_c^* . The values of ΔG_c^* were small unexpectedly, 2. 9 kJ/mol in the thymus and 5. 7 kJ/mol in the spleen.