The cover diagram shows a new family of pattern recognition molecules in humans, peptifoglycan recognition proteins (PGRP-L, PGRP-Ialpha, PGRP-Ibeta, and PGRP-S). They are differentially expressed in the liver, esophagus, and bone marrow, and they bind bacteria and bacterial cell wall peptidoglycan. They are conserved in evolution from insects to mammals, and they are likely to play a role in innate immunity to bacteria. Details can be found in the article by Liu et al., pages 34686-34694.34686.