Challenge with Pneumocystis carinii SCID mouse [91] Rat [119] Overexpression of interleukin-4 Mouse [120] SCID, severe combined immunodeficiency. and co-workers have recently confirmed the existence of polymorphisms at positions 11 and 160 of the mature protein [109] . The potential biological significance, if any, is not known. Interestingly, the 50 kDa variant of SP-D showed O-linked glycosylation of Thr11 [32 • ], suggesting that this polymorphism might be associated with altered glycosylation. Interestingly, the 50 kDa variant was recovered as trimeric subunits, raising the possibility that differences in the glycosylation of residue 11, which is immediately N-terminal to Cys15, could influence multimerization and the capacity of SP-D to participate in bridging interactions.