Generation of properdin^−/− mice. (A) Schematic representation of the mouse properdin gene locus. Vertical columns symbolize exon (E) locations. Horizontal rectangle box indicates the location of cDNA probe used for ES cell screening. (B) Targeting vector. Big arrowheads represent LoxP sites and small arrowheads represent FRT sites. Neo indicates neomycin; and DT, diphtheria toxin. (C) Actual recombinant properdin gene locus. (D) Expected restriction fragment lengths of wild-type and recombinant alleles. (E) Representative Southern blot screening result of ES cells after HincII and ScaI digestion. (F) Northern blot analysis of properdin mRNA in wild-type (WT) and properdin knockout (P^−/−) mouse tissues. (G) Immunodiffusion analysis of properdin in plasma. Antihuman properdin antibody was placed in the center well and mouse (10 μL) and human (5 μL) plasma or purified human properdin (0.5 μg) was placed in the peripheral wells. A precipitation line between the center and a peripheral well indicates the presence of properdin in the testing sample. (H) Western blot analysis showing the lack of properdin protein (P, ) in properdin^−/− mouse serum. The band below properdin represents goat IgG heavy chain used in immunoprecipitation. Purified human properdin (hP) was used as a positive control on the right lane. The size (in kDa) and position of molecular weight markers was shown on the left.