Although, the SP-A1 and SP-A2 variants exhibited major sex difference in most of the lung function studied after infection or in response to methacholine, the SP-A1/SP-A2 (6A2/1A0, co-ex) showed sex differences with Rrs, Rn, G, H, and Ers being increased and Crs being decreased in females compared to males after infection (Fig. 1), but this pattern changed after methacholine challenge (Fig. 4). The gene discussed is SFTPA2; the disease is infection.