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Lymfosyyttityypit refer to the different categories of lymphocytes, a crucial type of white blood cell within the immune system. Lymphocytes are responsible for adaptive immunity, meaning they recognize and remember specific pathogens, and mount a targeted response. The primary types of lymphocytes are B cells, T cells, and natural killer (NK) cells.

B cells are primarily involved in humoral immunity. Upon encountering an antigen, they differentiate into plasma cells that produce antibodies. These antibodies can neutralize pathogens directly or mark them for destruction by other immune cells. Some B cells also develop into memory B cells, which provide long-term immunity.

T cells are central to cell-mediated immunity and play a regulatory role in the immune response. There are several subtypes of T cells, including helper T cells (CD4+ T cells), which coordinate the immune response by activating other immune cells, and cytotoxic T cells (CD8+ T cells), which directly kill infected cells or cancer cells. Regulatory T cells help to suppress excessive immune responses and prevent autoimmunity. Like B cells, T cells can also form memory cells.

Natural killer (NK) cells are part of the innate immune system, though they are lymphocytes. They can recognize and kill stressed cells, virus-infected cells, and tumor cells without prior sensitization. NK cells achieve this by releasing cytotoxic granules that induce apoptosis (programmed cell death) in target cells. They also play a role in antibody-dependent cell-mediated cytotoxicity. Understanding the distinct functions of these lymphocyte types is fundamental to comprehending immune system activity and its role in health and disease.