The products of the KIR gene system are known to:

The products of the KIR gene system primarily function to detect self through HLA class I molecules. KIR, or Killer-cell Immunoglobulin-like Receptors, are a diverse group of receptors found on natural killer (NK) cells and some T cells. These receptors are crucial in immunological responses as they allow NK cells to recognize and respond to infected or transformed cells.

The interaction between KIR receptors and HLA class I molecules plays a vital role in the regulation of NK cell activity. KIR receptors can either activate or inhibit NK cell responses depending on the presence or absence of specific HLA class I molecules on target cells. In essence, this detection mechanism helps NK cells distinguish between healthy self-cells and potentially harmful cells that lack normal expression of HLA class I, which might indicate a viral infection or tumor transformation.

The other options do not accurately represent the functionality of the KIR gene system. For example, while some KIR receptors may show limited polymorphism, it is not correct to say they are non-polymorphic. Additionally, the KIR products are not homologous to HLA antigens, but rather, they interact with them. Lastly, detecting HLA-DRB4 null alleles does not pertain to