Identification of up-regulated proteins in the hemolymph of immunized Bombyx mori larvae

Insects defend themselves against foreign invaders via both a cellular response and a humoral response. The objective of this study was to identify proteins which were differently regulated in the immunized Bombyx mori larvae. Heat-inactivated bacteria (Bacillus megaterium) were injected into B. mori larvae, 4 days after final ecdysis. After 6 h, we identified the immune proteins in the hemolymph which had been differentially regulated in the immune-challenged larvae, using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and quadrupole time-of-flight (Q-TOF) tandem mass spectrometry (MS). After the bacterial injection, more than 30 spots determined to have been up-regulated, and 11 spots were down-regulated. The heat shock 70 kDa protein cognate was one of the up-regulated hemocytic proteins, and peptidoglycan recognition protein, antichymotrypsin precursor, and gloverin-like protein 1 approximately 4 were newly synthesized in the plasma. Antennal binding protein 7 was up-regulated in the plasma. Our results indicated that these immune response proteins were involved with the carrying out of innate immune responses.