Our Iowa Weed Laws

If all of us were good stewards of our land, we wouldn\u27t need weed laws. But experience has shown that we do need them, and the state legislature has provided them. Here\u27s how they work

Macrophage activation and Fcγ receptor-mediated signaling do not require expression of the SLP-76 and SLP-65 adaptors

The Src-homology 2 domain-containing, leukocyte-specific phosphoprotein of 76 kDa (SLP-76) is a hematopoietic adaptor that plays a central role during immunoreceptor-mediated activation of T lymphocytes and mast cells and collagen receptor-induced activation of platelets. Despite similar levels of expression in macrophages, SLP-76 is not required for Fc receptor for immunoglobulin G (IgG; FcγR)-mediated activation. We hypothesized that the related adaptor SLP-65, which is also expressed in macrophages, may compensate for the loss of SLP-76 during FcγR-mediated signaling and functional events. To address this hypothesis, we examined bone marrow-derived macrophages (BMM) from wild-type (WT) mice or mice lacking both of these adaptors. Contrary to our expectations, SLP-76-/- SLP-65-/- BMM demonstrated normal FcγR-mediated activation, including internalization of Ig-coated sheep red blood cells and production of reactive oxygen intermediates. FcγR-induced biochemical events were normal in SLP-76-/- SLP-65-/- BMM, including phosphorylation of phospholipase C and the extracellular signaling-regulated kinases 1 and 2. To determine whether macrophages functioned normally in vivo, we infected WT and SLP-76-/- SLP-65-/- mice with sublethal doses of Listeria monocytogenes (LM), a bacterium against which the initial host defense is provided by activated macrophages. WT and SLP-76-/- SLP-65-/- mice survived acute, low-dose infection and showed no difference in the number of liver or spleen LM colony-forming units, a measure of the total body burden of this organism. Taken together, these data suggest that neither SLP-76 nor SLP-65 is required during FcγR-dependent signaling and functional events in macrophages