Final answer:
In the innate immune response, scavenger receptors, dectin-1, the alternative pathway of complement activation, defensins, and the lectin pathway of complement activation are components that immediately engage in fighting infections.
Step-by-step explanation:
The innate immune system provides a rapid, non-specific response to pathogens through various mechanisms, some of which are immediate, and others that are induced. The components that participate in an immediate innate immune response to infection in a human host are as follows:
- scavenger receptors
- commensal microorganisms
- dectin-1
- alternative pathway of complement activation
- defensins
- CXCL8
- NOD1 and NOD2
- lectin pathway of complement activation
Scavenger receptors and dectin-1 are pattern-recognition receptors that identify and bind to components commonly found in pathogens, leading to their destruction. The alternative and lectin pathways of complement activation are part of the complement system, which can be triggered without prior exposure to the pathogen, thereby acting immediately. Defensins are antimicrobial peptides that can directly disrupt the pathogen's membrane. Commensal microorganisms, while part of the innate immunity, they contribute to host defense more by competitive exclusion of pathogens rather than immediate response to infection, while CXCL8, NOD1, and NOD2 are involved in signaling processes that can be viewed as induced.
Thus, the correct options that participate in an immediate response are: (a) scavenger receptors, (b) commensal microorganisms, (c) dectin-1, (d) alternative pathway of complement activation, (g) defensins, and (i) lectin pathway of complement activation.