group of endocrine disorders, where there appears to be a decreased hormonal level while in fact it is the receptor that is not responding sufficiently to the hormone. in the immune system main article: immune receptor the main receptors in the immune system are pattern recognition receptors (prrs), toll-like receptors (tlrs), killer activated and killer inhibitor receptors (kars and kirs), complement receptors, fc receptors, b cell receptors and t cell receptors.