The CR3 cytoplasmic tail is critical for serum opsonin-mediated immune suppression in human macrophages.

<p>(A) CHO cells stably expressing full length CR3 or a tail less mutant form of the receptor were transiently transfected with functional TLR2 and subsequently infected with serum pre-opsonized or non-opsonized <i>Ft</i> Schu S4 at an MOI of 50∶1 for different time points. Cell lysates were used to examine for ERK, p38 and Akt activation by Western blot using phosphor-specific antibodies. The same membrane was re-probed with total ERK, p38 and Akt as loading controls. The lower panel shows the band intensities measured by Image J software. (B) Cell association was quantified as the number of bacteria per cell by immunofluorescence microscopy using mouse <i>Ft</i> LPS antibody followed by Alexa Fluor 488. At least 300 cells were counted for every sample. Data are representative of 2 independent experiments performed in triplicate.