Ch 1 Introduction to the Immune System Flashcards
What are the two types of adaptive immunity, and what types of microbes do these adaptive immune responses combat?
The two types of adaptive immunity are cell-mediated immunity and humoral immunity. Cell-mediated immunity, mediated by T cells, is essential for protection against intracellular pathogens. Humoral or antibody-mediated immunity provides protection primarily against extracellular pathogens.
What are the principal classes of lymphocytes, and how do they differ in function?
B lymphocytes express surface immunoglobulin, which functions as their antigen receptor, and mediate humoral immunity. Following activation, lymphocytes differentiate into antibody-secreting plasma cells. T lymphocytes express the T cell antigen receptor and most express CD4 or CD8, and mediate cell-mediated immune responses. After activation by peptide antigens displayed by cell surface MHC molecules, T cells secrete cytokines, membrane-bound activating ligands, and cytotoxic proteins. These molecules induce inflammation, enhance the functions of phagocytes, promote B cell antibody responses, and induce death of infected cells.
What are the important differences among naive, effector, and memory T and B lymphocytes?
Naive lymphocytes are mature B or T cells that have not yet encountered a foreign antigen. Following activation, naive lymphocytes differentiate into cells that acquire the ability to protect against or eliminate pathogens. These lymphocytes are known as effector cells. Most effector cells die, but a small subset of activated lymphocytes acquires the ability to live for extended periods, known as memory cells. Memory lymphocytes not only self-renew and survive indefinitely but also respond more rapidly and vigorously when challenged by antigen.
Where are T and B lymphocytes located in lymph nodes, and how is their anatomic separation maintained?
B lymphocytes reside in follicles or B cell zones in secondary lymphoid organs. T cells reside in the T cell zone in the parafollicular cortex of lymph nodes. B and T cells are maintained in these locations by specific cytokines secreted by stromal cells in the follicle and the parafollicular cortex, respectively.
How do naive and effector T lymphocytes differ in their patterns of migration?
Naive lymphocytes home to secondary lymphoid organs and recirculate between these organs. Effector lymphocytes are generated in lymph nodes but home to the tissue site where the activating antigen may be located.
