Understanding the Immune System- Overview Flashcards
What is another name for lymphocyte?
White blood cell
What occurs in the thymus?
T-cells mature there
In what 4 areas are lymph nodes most commonly found?
Neck, armpit, groin and abdomen
What occurs in lymph nodes?
Immune cells congregate and encounter antigens
Where in the lymph nodes are B lymphocytes found?
Cortex/follicle
Where in the lymph nodes are antibodies produced?
In the germinal center
Where in the lymph nodes are T lymphocytes found?
Paracortex
Where in the lymph nodes are macrophages found?
In the medulla
Which cells are the main phagocytes involved in the first line of defense?
Macrophages and neutrophils
What are monocytes?
Monocytes are precursors to macrophages. They travel around in the blood and then migrate into the tissues where they mature into macrophages
What is the average lifespan of a neutrophil?
3 days.
What is the role of a neutrophil?
Neutrophils circulate the blood, and when tissue-based macrophages encounter an invader, neutrophils soon reinforce their immune response by coming to the site in large numbers
What are dendritic cells?
Dendritic cells are macrophage-like cells that are highly specialized for presentation of microbial antigens to lymphocytes
Name 3 lymphoid lineage cells.
Natural killer cells (NK cells), B-cells and T-cells
Name 6 myeloid lineage cells.
Eosinophils, basophils, dendritic cells, macrophages, monocytes and neutrophils (PMNs)
What do eosinophils defend against?
parasites
What do basophils defend against?
parasites- functions similar to eosinophils
What do neutrophils defend against?
general phagocytic cells of the innate immune system
What is the main role of dendritic cells?
Antigen presenting cells to lymphocytes
What is the responsibility of natural killer cells?
They provide innate immunity to viruses and tumors
What is the role of T-cells?
produce cytokines
What is the role of B-cells?
produces antibodies
What are “CD’s”?
Clusters of Differentiation- they are antigens expressed on the surface of specific subsets of immune cells- they are useful for differentiating cells types from one another
What is the CD specific for granulocytes?
CD15+
What is the CD specific for monocytes?
CD14+
What’s the CD specific to dendritic cells?
CD11c
What is the CD specific to t- cells
CD3+
What are the CDs specific to T-helper cells?
CD3+, CD4+
What are the CDs specific to cytotoxic T cells?
CD3+ and CD8+
What is the CD specific to B-cells?
CD19+
What is the CD specific to natural killer cells?
CD56+
What is the relative break down of white blood cells in the blood?
Neutrophils: 40-70% Lymphocytes: 20-50% Monocytes: 2-10% Eosinophils 1-% Basophils:
What is the general course of action for an antigen captured by a dendritic cell in peripheral tissue?
The Ag is phagocytosed by dendritic cells which traffic to regional lymph nodes. In the lymph node, the antigen is presented to the lymphocytes by the dendritic cells.
What happens to an Ag captured in the blood stream?
Ag is captured by the spleen and presented to lymphocytes in the spleen resulting in an immune response
What type of cells express class I MHC molecules?
Virtually all nucleated cells (no red blood cells)
Which cells express MHC class II ?
B-cells, monocytes, macrophages, dendritic cells
These also have class I MHCs as well
What are HLAs?
MHCs are called HLAs in humans
What is the purpose of MHC molecules?
They present foreign antigens to T-cells
What is the humoral response?
Humoral= B cell mediated
Antibodies produced by Ig-secreting B-cells (plasma cells) are directed against cell associated and free floating antigens
What is the cell-mediated response?
Cell-mediated = T-cells
Killing of cells by cytotoxic T-lymphocytes and/or production of cytokines directed against defective/infected cells and non-self cells.
What happens when an antibody on a b-cell in a lymph node binds to an antigen?
The B-cell clonally expands, differentiates and some of the clonally expanded cells become large plasma cells that produce identical copies of the antibody.
Memory b-cells are produced as well
What is a b-cell receptor?
BCR- antibody embedded in the plasma membrane of a b-cell, specific for an antigen
Which cells make cytokines?
T helper cells (CD4+)
What is the general role of a cytokine?
Growth, differentiation, and activation molecules that activate many immune cells, including b cells and other t-cells
What is the role of cytotoxic T-cells?
CD8+ cytotoxic T-cells help rid the body of cells that have been infected by viruses as well as cells that have been transformed by cancer. They can also reject tissue and organ grafts
How do natural killer cells and cytotoxic T cells kill their target?
They deliver bursts of lethal chemicals- perforin and granzymes
What happens to an antigen that is bound by an antibody?
It is marked for destruction by compliment and other immune cells
Describe the difference between a primary and secondary response.
Primary: modest
Secondary: Faster, bigger, longer due to expansion of memory cells –> much more antibody produced
How is a B-cell activated?
BCRs bind to their antigen –> antigen is engulfed and processed, and b-cells undergo clonal expansion and differentiation. Requires cytokines produced by antigen activated T-helper cells.
How are helper T-cells activated and what happens next?
An antigen from a class II MHC specific to a TCR binds and activates the T-cell. The helper t cell produces cytokines that increase the number of specific antibody producing plasma cells and the cytotoxic killer cells needed to quell the infection
How are cytotoxic T cells activated?
They bind to their specific antigens on Class I MHC molecules.
A resting cytotoxic T cell recognizes a virus fragment which is displayed by a dendritic cell or macrophage in combination with Class I MHC
