1. Differentiate between the primary and secondary lymphoid organs. Lymphoid organs form part of the body’s immune system. Lymphoid organs defend the body against invading pathogens that cause infections or spread of tumors. These organs exist as primary, secondary or tertiary, based on the stage of lymphocyte development and maturation the organ is involved in. The primary lymphoid organs serve to generate lymphocytes from immature progenitor cells. Progenitor cells possess the capacity to differentiate into a specific cell type. Progenitor cells divide for a limited number of times, depending on the need of the body. While, secondary lymphoid organs take charge of maintaining mature but naive lymphocytes. These organs initiate adaptive immune response. Examples of secondary or peripheral lymphoid organs include adenoids, the tonsils, lymph nodes, peyer’s patches, the spleen, and even the skin, among others.
2. Differentiate between polymorphonuclear and mononuclear cells. Polymorphonuclear cells are cell containing many nuclei. It that has granules (small particles) with enzymes that are released during infections, allergic reactions, and asthma. Neutrophils, eosinophils, and basophils are polymorphonuclear leukocytes. While, mononuclear cells are any cell that has a single round nucleus; for example, lymphocyte, monocyte. These cells are a critical component of the immune system to help fight infection.
3. Describe the functions of b and t lymphocytes.
B-lymphocytes are direct antigen recognition, differentiation into antibody-producing plasma cells and also involves in antigen presentation within class ii MHC. While t-lymphocytes involved in both humoral and cell mediated response, recognizes antigen presented within class ii MHC and promotes differentiation of b-cells and cytotoxic T-cells.
4. Give examples and functions of cells classified as ‘antigen presenting cells’. An antigen-presenting cell (APC) or accessory cell is a cell that displays foreign antigen complexes with MHC on their surfaces. Examples are dendritic cells, macrophages and epithelial cells.
5. Describe the format/type of antigen recognized by B lymphocytes, helper
T lymphocytes and cytolytic T lymphocytes.
B lymphocytes| Recognizes antigen presentation within class II MHC| Helper T lymphocytes| Recognizes antigen presented within class II MHC| Cytolytic T lymphocytes| Recognizes antigen presented within class I MHC|