title: The specificity of immune priming in silkworm, Bombyx mori, is mediated by the phagocytic ability of granular cells.
abstract: In the past decade, the phenomenon of immune priming was documented in many invertebrates in a large number of studies; however, in most of these studies, behavioral evidence was used to identify the immune priming. The underlying mechanism and the degree of specificity of the priming response remain unclear. We studied the mechanism of immune priming in the larvae of the silkworm, Bombyx mori, and analyzed the specificity of the priming response using two closely related Gram-negative pathogenic bacteria (Photorhabdus luminescens TT01 and P. luminescens H06) and one Gram-positive pathogenic bacterium (Bacillus thuringiensis HD-1). Primed with heat-killed bacteria, the B. mori larvae were more likely to survive subsequent homologous exposure (the identical bacteria used in the priming and in the subsequent challenge) than heterologous (different bacteria used in the priming and subsequent exposure) exposure to live bacteria. This result indicated that the B. mori larvae possessed a strong immune priming response and revealed a degree of specificity to TT01, H06 and HD-1 bacteria. The degree of enhanced immune protection was positively correlated with the level of phagocytic ability of the granular cells and the antibacterial activity of the cell-free hemolymph. Moreover, the granular cells of the immune-primed larvae increased the phagocytosis of a previously encountered bacterial strain compared with other bacteria. Thus, the enhanced immune protection of the B. mori larvae after priming was mediated by the phagocytic ability of the granular cells and the antibacterial activity of the hemolymph; the specificity of the priming response was primarily attributed to the phagocytosis of bacteria by the granular cells.
authors.affiliation: School of Chemistry and Chemical Engineering, Guangdong Pharmaceutical University, Zhongshan 528458, China.
authors.forename: Gongqing
authors.initials: G
authors.lastname: Wu
authors.affiliation: University of Electronic Science and Technology of China Zhongshan Institute, Zhongshan 528402, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Guangdong Pharmaceutical University, Zhongshan 528458, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: The First Affiliated Hospital of Clinical Medicine of Guangdong Pharmaceutical University, Guangzhou 510080, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Ding
authors.affiliation: School of Chemistry and Chemical Engineering, Guangdong Pharmaceutical University, Zhongshan 528458, China. Electronic address: Yunhongyi@163.com.
authors.forename: Yunhong
authors.initials: Y
authors.lastname: Yi
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology*; D012831:Bombyx / Q000276:immunology* / Q000382:microbiology; D006458:Hemolymph / Q000276:immunology; D007113:Immunity, Innate; D007814:Larva / Q000276:immunology / Q000382:microbiology; D010587:Phagocytosis; D020637:Photorhabdus / Q000235:genetics / Q000502:physiology*
keywords: Antibacterial activity; Bombyx mori; Granular cells; Immune priming; Phagocytosis