Similarity and diversity in macrophage activation by nematodes, trematodes, and cestodes

Abstract

This review summarizes current knowledge of macrophages in helminth infections, with a focus not only on delineating the striking similarities in macrophage phenotype between diverse infections but also on highlighting the differences. Findings from many different labs illustrate that macrophages in helminth infection can act as anti-parasite effectors but can also act as powerful immune suppressors. The specific role for their alternative (Th2-mediated) activation in helminth killing or expulsion versus immune regulation remains to be determined. Meanwhile, the rapid growth in knowledge of alternatively activated macrophages will require an even more expansive view of their potential functions to include repair of host tissue and regulation of host metabolism.

Figure 1

RELMα and YM1/2 expression in the pleural cavity during L. sigmondontis infection. Left-hand plots: Flow cytograms depicting side scatter (SSC) versus RELMα (a) or Ym1/2 (b) of pleural cavity cells 12 days post infection with L. sigmodontis. The gates for RELMα⁺ and Ym1/2⁺ cells were set using isotype control staining. The proportion of cells positive for RELMα and Ym1/2 in naïve mice was 1.5% and 0.05%, respectively. Right-hand plots: Siglec-F versus F4/80 expression on Ym1/2⁺ or RELMα⁺ cells. Numbers in italics represent percentage of cells within the neighbouring gate.