What type of cell is able to bind to certain tumor cells and virus-infected cells without specific antigen stimulation?

Natural killer cells play a crucial role in the innate immune response, allowing them to engage and eliminate tumor cells and virus-infected cells without the need for specific antigen recognition. They are a type of lymphocyte that can recognize stressed cells in the absence of antibodies and major histocompatibility complex (MHC) molecules, which typically mediate the adaptive immune response. This ability enables natural killer cells to act swiftly in the body’s defense against malignancies and infections, providing a first line of defense before the more specific adaptive immune mechanisms are activated.

In contrast, B cells require specific antigens to activate and produce antibodies, while cytotoxic T cells are dependent on the recognition of specific antigens presented by MHC molecules. Helper T cells also rely on antigen presentation to assist in activating other immune cells but do not directly target and kill infected or tumor cells. Thus, the unique function of natural killer cells in targeting cells lacking proper stimulation is what distinguishes them in this context.