Biochemical and functional characterization of three activated macrophage populations

Abstract

Abstract We generated three populations of macrophages (Mφ) in vitro and characterized each. Classically activated Mφ (Ca-Mφ) were primed with IFN-γ and stimulated with LPS. Type II-activated Mφ (Mφ-II) were similarly primed but stimulated with LPS plus immune complexes. Alternatively activated Mφ (AA-Mφ) were primed overnight with IL-4. Here, we present a side-by-side comparison of the three cell types. We focus primarily on differences between Mφ-II and AA-Mφ, as both have been classified as M2 Mφ, distinct from Ca-Mφ. We show that Mφ-II more closely resemble Ca-Mφ than they are to AA-Mφ. Mφ-II and Ca-Mφ, but not AA-Mφ, produce high levels of NO and have low arginase activity. AA-Mφ express FIZZ1, whereas neither Mφ-II nor Ca-Mφ do. Mφ-II and Ca-Mφ express relatively high levels of CD86, whereas AA-Mφ are virtually devoid of this costimulatory molecule. Ca-Mφ and Mφ-II are efficient APC, whereas AA-Mφ fail to stimulate efficient T cell proliferation. The differences between Ca-Mφ and Mφ-II are more subtle. Ca-Mφ produce IL-12 and give rise to Th1 cells, whereas Mφ-II produce high levels of IL-10 and thus, give rise to Th2 cells secreting IL-4 and IL-10. Mφ-II express two markers that may be used to identify them in tissue. These are sphingosine kinase-1 and LIGHT (TNF superfamily 14). Thus, Ca-Mφ, Mφ-II, and AA-Mφ represent three populations of cells with different biological functions.

Keywords

Affiliated Institutions

• University of Maryland, College Park US

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