Immune System Flashcards
Spleen’s function in immune system
Location of blood storage and activation of B-cells, which turn into plasma cells to produce antibodies as part of adaptive immunity.
Also acts as a storage area for white blood cells and platelets, and a filter of blood and lymph for the immune system.
Gut-associated lymphoid tissue (GALT)
Immune tissue found in close proximity to the digestive system, and is a site of potential invasion by pathogens.
Includes tonsils and adenoids in the head, Peyer’s patches in the small intestine, and lymphoid aggregates in the appendix.
Hematopoietic stem cells
Give rise to granulocytes and agranulocytes, and gives rise to red blood cells and platelets.
Defensins
Antibacterial enzymes found on the skin.
Complement system
Consists of a number of proteins in the blood that act as a nonspecific defense against the bacteria.
How can the complement system be activated
Through a classical pathway (which requires the binding of an antibody to a pathogen) or an alternative pathway (which does not require antibodies).
How does complement system work
Complement proteins punch holes in the cell walls of bacteria, making them osmotically unstable. Considered nonspecific defense because it cannot be modified to target a specific organism over others.
Interferons
Proteins that prevent viral replication and dispersion, and are produced by cells that have been infected with viruses.
Interferons also upregulate MHC class I and class II molecules, resulting in increased antigen presentation and better detection of the infected cells by the immune system.
Also responsible for many “flu-like” symptoms.
What are the 3 things an activated macrophage does.
- It phagocytizes the invader through endocytosis.
- Digests invader using enzymes
- Presents little pieces of invader (mostly peptides) to other cells using a protein called major histocompatibility complex (MHC).
Major histocompatibility complex (MHC)
Binds to a pathogenic peptide (antigen) and carries it to the cells surface, where it can be recognized by cells of the adaptive immune system. Comes in class I and II
MHC class I molecules
Present in all nucleated cells in the body. Only those cells that are infected would be expected to present an unfamiliar (nonself) protein on their surfaces.
The MHC-I pathway is often called what, and why
Often called the endogenous pathway because it binds antigens that come from inside the cell.
MHC class II molecules
Mainly displayed by professional antigen-presenting cells like macrophages. They pick up pathogens from the environment, process them, and then present them on MHC-II.
THe MHC II pathway is often called what, and why
The exogenous pathway, because these antigens originated outside the cell.
Pattern recognition receptors (PRR), including toll-like receptors (TLR)
Receptors present on macrophages and dendritic cells that are able to recognize the category of the invader (bacterium, virus, fungus, or parasite).
Natural killer (NK) cells
A type of nonspecific lymphocyte that is able to detect the downregulation of MHC and induce apoptosis in virally infected cells.
Neutrophils
Most populous leukocyte in blood –> phagocytic and target bacteria using chemotaxis. Dead neutrophil collections responsible for pus formation
Eosinophils
Contain bright red-orange granules and are primarily involved in allergic reactions and invasive parasitic infections. –> release histamine
Basophils
Contain large purple granules and are involved in allergic responses –> least populous leukocyte in bloodstream under normal conditions
Mast cells
Closely related to basophils, but have smaller granules and exist in tissues, mucosa, and epithelium. Also release histamines.
