Lymphocytes are a group of white
blood cells (leukocytes) that are produced in the bone marrow. They are present in the blood, lymph, connective
tissue and lymphoid organs such as lymph nodes, spleen, tonsils, adenoids and Peyer's patches. The lymphocytes
play a major role in immune responses: humoral immunity response, associated with the production of antibodies;
and cellular immunity, associated with proliferation of effector cells - a specific group of cells in the immune
system that response to stimulus.
In healthy people, there
are 4,500-10,000 white blood cells per microliter (mcL). The number varies depending on age and certain
medications. For instance, the number increases in case of infections or inflammation. However, despite the
increase of blood cells in a healthy person, lymphocytes represent 20 to 40% of white blood cells. Normally, the
number of lymphocytes permilliliter (ml) must
than 4000 in adults
than 7 000 in children
than 9 000 in an infant.
All these white cells go
through a predictable life cycle - they naturally die (when they become too old) to be replaced by new ones. In
the case of Non-Hodgkin's lymphoma, white blood cells can multiply excessively and, without going through this
natural death; this condition causes formation of cancer cells.