The Fc-AIM complex serves to prolong the half-life of AIM.

(A) The strategy for purification of the hFc-AIM complex. S: culture supernatant; F1 and E1: flow-through and eluent from the anti-hAIM monoclonal antibody column; F2 and E2: flow-through and eluent from the anti-FLAG (M1) antibody column. (B) 100 µg of hFc-AIM contains about 20 µg of hAIM. (C) 100 µg of purified hFc-AIM complex or 20 µg of purified hAIM was intravenously injected into wild-type (B6) mice, and the half-lives of the injected hAIM were compared by immunoblotting. Left: Injected hAIM (37 kDa) can be distinguished from endogenous mouse AIM (45 kDa) by molecular weight. Right: The values of hAIM were normalized so that the values at 1 h after injection corresponded to 100%. Red triangles and black circles represent the serum hAIM levels of the mice injected with hFc-AIM and hAIM alone, respectively. (D) Specimens of epididymal white adipose tissue from the obese AIM^−/− mouse administered 500 µg of hFc-AIM were stained for AIM (green) and F4/80 (red), and counterstained with Hoechst 33342 (blue). The crown-like structures formed by recruited macrophages are indicated by arrows. Different sections were stained for AIM (green) and IL-6 (red), as well as with HE.