Special Sub-Topic: Immunology Click Here To Play: Immunology

What are the two types of immunity?

adaptive, innate. The innate immunity carries out the initial response to pathogens and activates the adaptive immune system. The innate immunity is not specific and can respond to most, if not all, antigens. It does not provide long-lasting immunity. The adaptive immunity is highly specific and tailored to a specific antigen. It provides long-lasting immunity against the specific antigen.

Which of these are the most abundant in circulation?

neutrophils. Basophils make up less than 1% of total leukocytes (white blood cells). Mast cells are found in connective tissues and close to mucosal surfaces. Dendritic cells are found in tissues, lymph nodes, spleen and thymus.

Which of these is a professional antigen presenting cell (APC)?

dendritic cells. A professional antigen presenting cell specializes in processing antigens into smaller pieces to be presented to lymphocytes so that an immune response can be initiated. Dendritic cells ingest antigens and degrade them into peptides. The peptides are fused with MHC Class II molecules and presented to T cells. Other professional APC include macrophages and B cells.

Which of these is a secondary lymphoid organ?

Spleen. A secondary lymphoid organ is an organ or site where lymphocytes (eg. B cells, T cells) migrate to so that they can encounter antigens and pathogens, in other words, germs. Other secondary lymphoid organs include the lymph nodes and mucosa-associated lymphoid tissue (MALT).

T cells require two signals to be activated. One signal is the binding of the antigen presented by the antigen presenting cell (APC). The other is the binding of

co-stimulators. Examples of co-stimulatory molecules are B7 and CD28, which are molecules expressed on the surface of T cells, APCs and B cells. These molecules must bind to each other to complete T-cell activation.

What kind of cells produce antibodies?

B cells. B cells begin to produce and secrete antibodies after being activated by T cells or antigens.

How are the different isotypes of antibodies produced?

class switching. After activation, some B cells will class switch to produce a different isotype of immunoglobulin. This is controlled by cytokines secreted by T helper cells. The five different isotypes of a particular antibody all have the same specificity for a particular antigen, but they function in different parts of the body such as mucosal surfaces, tissue or blood.

Which of these is an autoimmune disease?

All of these (Rheumatoid Arthritis, Graves Disease, Systemic Lupus Erythematosus (SLE)). Autoimmune diseases occur when the immune system fails to recognize the body's cells and tissue as "self" and initiates an immune response against the body's cells and tissue.

What can be a cause of immunodeficiencies?

All are correct. Immunodeficiency is a condition where the immune system fails to function properly resulting in increased susceptibility to infections or recurrent infections.

What is hypersensitivity?

Allergic reactions. Hypersensitivity is another name for allergic reactions. They happen when the immune system over-reacts against harmless antigens present in the environment.