CTSL and Mycoplasma pneumoniae pneumonia: To test these predictions, we investigated the preventive effects of recombinant CTSL (rCTSL) on mycoplasma pneumonia of swine which is the most approximate model to humans [31, 32], and the effects of rCTSL and native CTSL on SIgA responses and Ii degradations in the co-cultured dendritic cells (DCs) and B cells model in vitro.