Answer :
B cell receptors (BCRs) and T cell receptors (TCRs) are essential components of the adaptive immune response. They are responsible for the specific recognition of antigens, which are substances that the body identifies as foreign. Let's go through the process of how they distinguish one pathogen from another:
a. Pathogen-associated molecular patterns (PAMPs): These are molecules shared by multiple pathogens, but not usually found on host cells. They are recognized primarily by pattern recognition receptors (PRRs) of the innate immune system, not by BCRs or TCRs.
b. Macromolecules that are unique to a given pathogen: These macromolecules can be proteins, carbohydrates, fats, or nucleic acids that are unique to a specific pathogen. BCRs and TCRs recognize these unique macromolecules or epitopes on the antigens. Because these macromolecular structures are diverse and highly specific to each pathogen, BCRs and TCRs can discriminate between different pathogens effectively.
c. Pathogen-specific cytokines: Cytokines are small proteins that are important in cell signaling, and they can be produced in response to a pathogen. However, cytokines are not typically unique to individual pathogens in the way that antigens are. They are signals produced by cells, not something that BCRs or TCRs would recognize as antigens.
d. Damage-associated molecular patterns (DAMPs): Similar to PAMPs, DAMPs are host molecules that can initiate and perpetuate a noninfectious inflammatory response. They are released from damaged or dying cells, not directly from a pathogen, and like PAMPs, they are recognized by cells of the innate immune system.
Based on the information above, the correct answer is:
b. Macromolecules that are unique to a given pathogen
This is due to the specificity of the BCRs and TCRs for particular antigenic structures that are found only on distinct pathogens, which allow these receptors to distinguish and respond to individual types of pathogens.