This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts, Subject name: Pathology
All of the following are pattern recognition receptors for extracellular/ingested microbes, except: 
Select and explain. 
A. Toll-like receptors (TLRs), B. Killer-cell immunoglobulin receptors (KIRs), C. NOD-like receptors (NLRs), D. C-type lectin receptors (CLRs)
B: Killer-cell immunoglobulin receptors (KIRs)
Answer: B: Killer-cell immunoglobulin receptors (KIRs) 
Explanation: Pattern recognition receptors Cells that paicipate in innate immunity are capable of recognizing ceain components that are shared among related microbes. Pattern recognition receptors are located in all cellular compaments where microbes may be present: plasma membrane receptors detect extracellular microbes, eg. Toll-like receptors (TLRs), C-type lectin receptors (CLRs). endosomal receptors detect ingested microbes, eg. Toll-like receptors (TLRs) cytosolic receptors detect microbes in the cytoplasm, eg. NOD-like receptors (NLRs), RIG-like receptors (RLRs) Killer-cell immunoglobulin-like receptors (KIRs), are present on plasma membrane of NK cells. KIR receptors can recognise major histocompatibility (MHC) class I variants, which allows NK cells to detect virally infected cells or transformed cells.