The cellular and humoral basis of the immune response.

Class II molecules, called Ia molecules or DR, are expressed in macrophages, B lymphocytes, and activated T cells. Through these molecules, the B and T cells produce the immune response. Furthermore, this class of glycoproteins can serve as markers for the immune responses and their related disorders, ie, autoimmune disease. The new discoveries of the extended haplotypes, which include the genes for some proteins of the complement system and the Ia-like genes, make it possible to study the association of a chromatin section of chromosome 6 (seven centimorgans) with diseases.