Immunology Flashcards
What is immunology?
A branch of biomedical sciences concersn with immunity or immune system
Study of host defence against infection
What is the immune system?
A complex network of organs, tissues, cells, and molecules that protect the body against infections and other diseases
What organs and tissues are associated with the immune system?
- Bone marrow
- Spleen
- Thymus
- Tonsils
- Mucous membranes
- Skin
- Lymphatic vessels and nodes
What cells are involved in the immune system?
- Lymphocytes (T-cells, B-cells, and NK-cells)
- Granulocytes (neutrophils, eosinophils, and basophils)
- Monocytes/macrophages
What are some characteristics of innate immunity?
- Non-adaptive (involves granulocytes, monocytes/macrophages)
- First line immune response (present at birth)
- Relying on mechanisms that exist before infections
- Rapid (within minutes) but non-specific
- Inflammation
What are some characteristics of acquired (adaptive) immunity?
- Second line immune response
- Can take several days to 1 week to allow body to develop its own antibodies
- T-cells and B-cells involved
- Developed from immunological memory
What are the different types of cells involved in innate immunity?
- NK cells
- Dendritic cells
- Mast cells
- Neutrophils
- Basophils
- Eosinophils
- Macrophages
What are some functions of NK cells?
Cytotoxic, kill infected cells and cancer cells
What are some functions of Dendritic cells?
Antigen-presenting, important to acquired immunity
What are some functions of Mast cells?
Rich in histamine and heparin, possess antibacterial and antiparasitic functions
Regulate inflammation (induce fever = increased bacterial death)
What are some functions of Neutrophils?
Patrol for microbial infections and one of the first responders to the site of inflammation
Antimicrobial WBCs
What are some functions of Basophils?
Fight parasite infections and mediate allergic reactions (less effective against bacterial infection)
What are some functions of Eosinophils?
Possess antibacterial and antiparasitic functions
What are some functions of Macrophages?
Phagocytosis and present antigens along with dendritic cells
What are the three innate immune response system mechanisms?
- Pattern recognition receptors (PRRs)
- Damage-associated molecular patterns (DAMPs)
- Detecting missing-self (mainly via NK cells)
How do pattern recognition receptors regulate the innate immune system?
They recognize specific pathogen fragments and initiate immune response
How do damage-associated molecular patterns (DAMPs) regulate the innate immune system?
Endogenous molecules released from damaged and dying cells during infection and inflammation
How does non-self detection regulate the innate immune system?
Recognizing molecules expressed in healthy cells inhibits immune response against healthy cells
The immune system detects non-self or diseased cells and mounts response
Review slide 8 for a summary of adaptive immunity
What are the two MHC molecules?
MHC (major histocompatibility complex) are essential for acquired immunity
MHC class I and II
What are some characteristics of MHC Class I molecules?
Identified in all nucleated cells
Present normal self-antigens and foreign pathogen antigens to cytotoxic T cells
What are some characteristics of MHC Class II molecules?
Identified in macrophages, dendritic cells and B cells
Present foreign pathogen antigens to helper T cells (CD4 cells)
Review slide 10 for differences between MHC Class I and II
What is the main cell type for cell-mediated immunity?
Antigen-specific cytotoxic T-cells (no antibody involvement)
Directly kill infected cells
What is the main cell type for humoral immunity?
B-cells (differentiate into memory B cell and plasma cells)
Mediated by secreted antibodies (5 different types)
What is the process for T-cell maturation?
- Hematopoietic stem cells in bone marrow mature into lymphoid progenitor cells and migrate to thymus
- Lymphoid progenitor cells mature and differentiate into functional T-cells (CD4 and CD8 cells)
see slide 13
What are the characteristics of CD4 T-cells?
They are helper T-cells, secrete cytokines to stimulate the differentiation of B cells into plasma cells
What are the characteristics of CD8 T-cells?
They are cytotoxic T-cells, bind and kill infected cells and cancer cells
What is the most common antigen-presenting cell type?
Dendritic cells
How are T-cells activated?
Activated by simultaneous interactions of surface molecules between cytotoxic (CD8) cells and antigen-presenting cell
First activation signal (TCR of CD8 and MHC I of APC)
Second activation signal (CD28 of CD8 and CD80/CD86
What are Regulatory T cells (Tregs)?
Specialized type of T cells (different from T helper cells)
Maintain immune homeostasis and self-tolerance (calms down immune system)
Can inadvertently promote cancer develop by inhibiting anticancer immunity
What are the ways B cell can be activated?
- Activated when B-cell receptor binds to antigen
- T-cell dependent activation
- T-cell independent activation
- Memory B-cell activation
see slide 18
What is the advantage of cell-mediated B cell activation?
Increased proliferation
What are the different classes of antibodies?
IgA, IgD, IgE, IgG, and IgM
What are some characteristics of IgA?
- Monomeric in serum
- Dimeric in GI tract (J chain binds the two IgA molecules)
- Major function (inhibit bacterial growth and neutralize bacterial toxins)
- Minor function (neutralize viruses, slower response)
What are some characteristics of IgD?
- Monomeric
- Usually co-expressed with IgM
- Target mucosal antigens (enhance mucosal immunity)
- Activate B-cells, basophils, and mast cells
What are some characteristics of IgE?
- Monomeric
- Mediate Type I hypersensitivity reactions
- Immunity against parasitic infections
What are some characteristics of IgG?
- Main type of antibody (about 75% of serum antibodies)
- Produced second, after IgM by humoral immunity response
- Bind different types of antigens, bacteria, and fungi
How is antibody production different in newborns?
Three of the four IgG subclasses can cross the placenta, so newborns have the same antibodies as their mothers during the first 6 months of life
What are the characteristics of IgM?
- Largest antibody (pentameric)
- It is the first antibody produced by humoral immune response
- May also present as hexamers (when J chain is missing)
See slide 26 for the IgM-IgG sequential response
