Site Map

Immune response

Special white blood cells called lymphocytes play a key role in the immune system's response to foreign invaders. There are two main groups, both of which form in bone marrow.

One group, called T-lymphocytes or T-cells, migrates to a gland called the thymus.

Influenced by hormones, they mature there into several types of cells, including helper, killer, and suppressor cells. These different types work together to attack foreign invaders. They provide what's called cell-mediated immunity, which can become deficient in persons with HIV, the virus that causes AIDS. HIV attacks and destroys helper T cells.

The other group of lymphocytes are called B-lymphocytes or B cells. They mature in the bone marrow and gain the ability to recognize specific foreign invaders.

Mature B cells migrate through the body fluids to the lymph nodes, spleen, and blood. In Latin, body fluids were known as humors. So B-cells provide what's known as humoral immunity. B-cells and T-cells both circulate freely in blood and lymph, searching for foreign invaders.


Review Date: 1/23/2022  

Reviewed By: Stuart I. Henochowicz, MD, FACP, Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

ADAM Quality Logo
Health Content Provider

A.D.A.M., Inc. is accredited by URAC, for Health Content Provider ( URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics. This site complied with the HONcode standard for trustworthy health information from 1995 to 2022, after which HON (Health On the Net, a not-for-profit organization that promoted transparent and reliable health information online) was discontinued.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2023 A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.