Immune responses of mussel hemocyte subpopulations are differentially regulated by enzymes of the PI 3-K, PKC, and ERK kinase families.
Various hemocyte cell types have been described in invertebrates, but for most species a functional characterization of different hemocyte cell types is still lacking. In order to characterize some immunological properties of mussel (Mytilus galloprovincialis) hemocytes, cells were separated by flow cytometry and their capacity for phagocytosis, production of reactive oxygen species (ROS), and production of nitric oxide (NO), was examined. Phosphatidylinositol 3-kinase (PI 3-K), protein kinase C (PKC), and extracellular signal-regulated kinase (ERK) inhibitors were also used to biochemically characterize these cell responses. Four morphologically distinct subpopulations, designated R1-R4, were detected. R1, R2, and R3 cells presented different levels of phagocytosis towards zymosan, latex beads, and two bacteria species. Similarly, R1 to R3, but not R4, cells produced ROS, while all subpopulations produced NO, in response to zymosan. Internalization of all phagocytic targets was blocked by PI 3-K inhibition. In addition, internalization of latex particles, but not of bacteria, was partially blocked by PKC or ERK inhibition. Interestingly, phagocytosis of zymosan was impaired by PKC, or ERK inhibitors, only in R2 cells. Zymosan-induced ROS production was blocked by PI 3-K inhibition, but not by PKC, or ERK inhibition. In addition, zymosan-stimulated NO production was affected by PI 3-K inhibition in R1 and R2, but not in R3 or R4 cells. NO production in all cell types was unaffected by PKC inhibition, but ERK inhibition blocked it in R2 cells. These data reveal the existence of profound functional and biochemical differences in mussel hemocytes and indicate that M. galloprovincialis hemocytes are specialized cells fulfilling specific tasks in the context of host defense.
Department of Immunology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City DF-04510, Mexico.
Erick
E
García-García
Maria
M
Prado-Alvarez
Beatriz
B
Novoa
Antonio
A
Figueras
Carlos
C
Rosales
D000818:Animals; D002469:Cell Separation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D006434:Hemocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology*; D007113:Immunity, Innate; D049878:Mytilus / Q000201:enzymology / Q000276:immunology*; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology* / Q000378:metabolism; D011493:Protein Kinase C / Q000276:immunology* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D015054:Zymosan / Q000378:metabolism
D017382:Reactive Oxygen Species; D015054:Zymosan; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases