Lymphocytes

Lymphocytes are the smallest leukocytes and are similar in size to red blood cells (generally 6-9 μm, although they can be larger). 20-40 % six to nine micrometers, although they can be larger). Twenty to forty percent of white blood cells are lymphocytes.

Lymphocytes can be recognized by their large, single, round nucleus which fills most of the cell’s volume (although a thin rim of cytoplasm is always present). When stained using an alkaline dye, the nucleus stains dark purple owing to the high concentration of nucleic acid inside. As agranulocytes, lymphocytes lack any granules in their cytoplasm.

The primary functions of lymphocytes:

• Providing specific or adaptive immunity with some living for several years and contributing to "immune memory".

• Lymphocytes can recognize "foreign" antigens presenting on the surface of infected or invading cells.

• Producing specific antibodies in response to a recognized pathogen.

• Destroying infected cells.

• Regulating and coordinating immune responses.

Figure 1. Lymphocyte