What is the primary feature of a naïve B-cell's receptor?

The primary feature of a naïve B-cell's receptor is that it has a unique antibody-binding region. Each naïve B-cell is equipped with a B-cell receptor (BCR) that is specific to a distinct antigen. This specificity is a result of the unique structure of the antibody-binding region, which varies among different B-cells. This allows the immune system to recognize a diverse array of antigens. The BCR is essentially a membrane-bound form of an antibody, and its variation is crucial for the adaptive immune response, enabling the body to target and remember a specific pathogen during future exposures.

In contrast, other options do not accurately represent the characteristics of naïve B-cell receptors. While B-cells can have similar features within a certain clone, they do not have receptors that are identical across all B-cells, as immunological diversity is essential for effective immune responses. The idea of binding multiple antigens at once does not apply to the specific binding requirement of BCRs, which are designed to engage with one particular antigen at a time. Lastly, saying that it lacks specificity is misleading, as the BCR's unique antibody-binding region is what imparts its specificity to particular antigens.