Lymphocytes - about 25% of wbc, these cells come in B and T cell types (see Immune System Notes) and are responsible for the specific immune response. Lymphocytes acquire immunocompetence in the thymus and other areas and subsequently proliferate by cloning in the lymph nodes. They circulate between the lymph, circulation, lymph and back again for long periods of time.
	Lymphocytes come in small, medium, and large varying in diameter from 6 to 18m. Most are recirculating immunocompetent cells. T-cell lymphocytes are responsible for cell-mediated immunity, while B-cell lymphocytes secrete antibodies (humoral immunity).