Furthermore, since CD40-CD40L deficiency can result in immunodeficiency in humans, blocking this pathway might have resulted in adverse events such as an undefined infection that could result in weight loss or lack of weight gain. Although a consideration, it is less likely due to the extensive efforts maintained to minimize infections in the vivarium. Interestingly, the reduction of T cell activation was associated with a reduction in pro-inflammatory macrophages. The one caveat to that was the reduction in macrophages seen in mice given the IgG protein, where they actually had an increase in activated CD8+ T cells. We believe the reduced pro-inflammatory macrophage count was due to a separate mechanism. Intravenous immunoglobulin is a therapy used for autoimmune disorders, where overwhelming the system with AZD6244 non-pathogenic antibody appears to elicit a beneficial response, an effect that may be Fc receptor mediated. In our study, we believe that the Fc DAPT receptors on macrophage are being affected by the Fc region on the non-pathogenic IgG protein. This is not an issue for CTLA- 4 Ig, since the Fc region of the molecule is mutated and cannot bind the Fc receptors in the mouse. The reason this is not an issue for the anti-CD40L antibody, MR1, is that the antibody does not activate the mouse Fc receptor. So these observations are unique to the IgG protein, whereas the observations with the other proteins are likely due to the reductions in T cell activation. This effect of the control IgG protein is speculative since the use of IVIG involves high doses of protein that contain multiple IgG isotypes. A limitation of our study was the lack of a saline injection control, as we expected the IgG to be our control. However, we did have the untreated mice for comparison. Another limitation is that we did not differentiate between Th1 and Th2 CD4+ T cells, since differences in CD4+ T cell activation were observed between our two co-stimulatory blockers. In the CTLA-4 Ig group, we saw decreased CD4+ T cell activation, which could be due to a reduction of either Th1 and/or Th2 cells. In the anti-CD40L group, we saw an increase in the activated CD4+ T cells. Since the treatment was seemingly beneficial, we can presume this represents an increase in the anti-inflammatory Th2 cells. An additional interesting finding was the effect of anti-CD40L antibody on cholesterol levels in mice fed the obesogenic diet, the reason for which is not immediately apparent. There appears to be a link between inflammation and cholesterol metabolism seen in other studies of mice lacking TLR4 and CD180, two molecules that are involved with propagation of inflammatory signals. Blocking inflammation by various mechanisms may interfere with cholesterol metabolic pathways in a yet undiscovered manner. This is an area that needs further exploration. Other interesting findings in this study include the increased FoxP3+ CD4+ T regulatory cells in adipose tissue from untreated obese mice versus lean chow fed mice, which were subsequently decreased further in the CTLA-4 Ig group and unchanged in the anti-CD40L group. This contradicts previous reports that suggest T regulatory cells decrease in obesity. Since T regulatory cells are anti-inflammatory, it would make theoretical sense that they try to dampen the inflammatory response during obesity, but may not be able to overcome that challenge. CTLA-4 Ig is known to reduce T regulatory cell activation when used alone, which might explain the finding in this study. However, the use of CTLA-4 Ig in combination with anti-CD40L can result in an induction of T regulatory cells.