Lymphocytes are a crucial component of the immune system, particularly in the context of adaptive immunity. The two primary types of lymphocytes involved in this process are T cells and B cells. These cells are characterized by their ability to respond to specific antigens presented by invading microbes, which is a defining feature of adaptive immunity.

In contrast to T cells and B cells, there exists a group of lymphocytes known as innate lymphoid cells (ILCs). Unlike their adaptive counterparts, ILCs do not exhibit specificity in antigen recognition. A notable example of ILCs is natural killer (NK) cells, which play a role in innate immunity by targeting a variety of cell types without the need for specific antigen recognition.

To summarize, while T cells and B cells are integral to adaptive immunity and are highly specific in their responses, innate lymphoid cells, including NK cells, are part of the innate immune response and lack this specificity. Understanding the distinction between these cell types is essential as we delve deeper into the mechanisms of the immune system throughout the course.