Innate Immune Gene Expression in Immunocompromised Versus Immunocompetent Zebrafish
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Many bacteria live commensally in the intestines of complex host organisms. but the methods by which this community assembles are not fully understood. It is :i.uspected that two processes, inter-host dispersal and host selection, play a role. Host selection is thought to be dictated by the immune system; however the role of the immune system in commensal host-microbe interactions is not well understood. This experiment examines the aclivily of the innate immune system in the context of interhost dispersal and bacterial community assembly. To carry out this experiment. WildType (WT) fish and myd8S-1• fish. which were missing a key protein in the TLR pathways. were housed at different levels exposure to inter-host dispersal. l found that the immunocompromised 111yd8ir1• fish had significantly lower levels of TLR-pathway dependent IL 18 expression, but that activity of TLR-inclependent protein CJ was unaffected. lmmunocompromiscd fish also demonstrated lower survival rates, and also developed less when in competition with WT fish for resources in the cohoused situation. Greater levels of host dispersal also increased the difference in activity level ii iii between genotypes. These results suggest that innate immune activity is impacted by inter-host dispersal and by the presence of a commensal bacterial community.