Adaptive Immunity Flashcards
What are the three general aspects of adaptive immunity?
Systemic effect, Specificity, Memory
What is cellular (cell-mediated) immunity?
- Lymphocytes directly attack and destroy foreign cells or diseased host cell
- Rids the body of pathogens that reside inside human cells
- Kills cells that harbor them
What is humoral (antibody-mediated) immunity?
- Mediated by antibodies that do not directly destroy a pathogen but tag it for destruction
- Many antibodies are dissolved in body fluids
- Effective against extracellular viruses, bacteria, yeasts, protozoans, and molecular disease agents such as toxins, venoms, and allergens.
What is an antigen?
Any molecule that triggers an immune response - characteristics enable body to distinguish “self” molecules from foreign ones.
What are epitopes (antigenic determinants)?
Certain regions of an antigen molecule that stimulate immune responses - one antigen molecule typically has several epitopes that can stimulate the simultaneous production of different antibodies.
What do haptens do?
Trigger immune response by combining with a host marcomolecule and creating a complex that the body recognizes as foreign.
What are antibodies?
Antibodies, also known as immunoglobulins, are a defensive gamma globulin found in blood plasma, tissue fluid, body secretions, and some leukocyte membranes.
Describe the structure of a antibody monomer.
Composed of four polypeptide chains linked by disulfide bonds. Two larger heavy chains have a hinge region where antibody is bent. Two light chains gives the antibody its uniqueness. Constant
Describe the antigen-binding site.
Formed from the V regions of the heavy and light chain on each arm. Attaches to the epitope of an antigen molecule.
Somatic recombination
DNA segments shuffled and form new combinations of base sequences to produce antibody genes.
Somatic hypermutation
B cells in lymph nodules rapidly mutate creating new sequences
What are the three types of lymphocytes?
Natural kill (NK) cells, T lymphocytes (T cells), B lymphocytes (B cells)
Describe positive selection (T cells)
Positive selection testes CD4+ and CD8+ thymocytes to determine if they bind to major histocompatibility complex (MHC) class 1 or MHC class 2 molecules, displayed on thymic epithelial cells. (CD8+ binds to MHC class 1& CD4+ binds to MHC class ). Occurs in thymus cortex.
Describe negative selection (T cells)
Negative selection tests the ability of CD4+ and CD8+ thymocytes to tolerate self-antigens. Thymic dendritic cells display self-antigens on MHC complexes. Thymocytes that bind self-antigens with their TCRs are destroyed, while surviving thymocytes continue maturing. Occurs in the medullary region of the thymus.
What are antigen-presenting cells?
A cell that phagocytizes an antigen and displays fragments of it on its surface for recognition by other cells of the immune system; chiefly macrophages and B lymphocytes - T cells cannot recognize antigens on their own.
