Chronic, low-grade inflammation of visceral adipose tissue, and systemically, is a critical link between recent strikingly parallel rises in the incidence of obesity and type 2 diabetes. Macrophages have been recognized for some time to be critical participants in obesity-induced inflammation of adipose tissue. Of late, a score of other cell types of the innate and adaptive arms of the immune system have been suggested to play a positive or negative role in adipose tissue infiltrates. This piece reviews the existing data on these new participants; discusses experimental uncertainties, inconsistencies, and complexities; and puts forward a minimalist synthetic scheme. Copyright © 2013 Elsevier Inc. All rights reserved.