SP-D can be isolated in different multimeric forms from proteinosis lavage [32 • ] and are produced by Chinese hamster ovary K1 cells transfected with human SP-D cDNA [18] . As described previously, the effects of SP-D on the neutrophil response to influenza virus are highly dependent on the ability of SP-D to agglutinate the viral particles, and the agglutination activity is directly correlated with the extent of multimerization. Trimers can bind to the virus but have little capacity to modulate neutrophil interactions. By contrast, highly multimerized proteins show greater activity than dodecamers [81] .