Lecture 3 and 4 Acquired Immunity Flashcards
What are features of Acquired Immunity?
- Specificity of antigen
- Versatility - ready to confront any antigen at any time
- Memory - “remembers antigens that it has confronted
- Tolerance - responds to foreign substances but ignores normal tissues
How do B and T lymphocytes have specificity and versatility?
- Each B and T lymphocyte binds to a specific pathogen epitope
- Specificity also means different receptors per B and T cell
What is the clonal selection, expansion and memory theory?
Clonal selection theory is how naive lymphocyte reproduction is favored in strong binding between antigens and lymphocytes which leads to production of antibody secreting plasma cells and memory cells
What is faster, Primary or Secondary immune response
Secondary
Where do B and T lymphocytes originate
- Both originate from bone marrow as hematopoietic stem cells
- T cells undergo positive and negative selection in the thymus
- B cells undergo positive and negative selection in the bone marrow
How are B cells activated?
- Antigen binds to specific B cell
- Antigen internalized, digested and antigen binds to MHC while internalized
- MHC with antigen is then transported to cell surface
- Specific helper T cell recognizes antigen and MHC becomes activated secreting cytokines
- Activated B cells divide and cytokines help produce plasma cells and memory cells
How do antibodies protect us?
- Activate B lymphocytes
- Acts as opsonin
- Causes antigen clumping and inactivation of bacterial toxins
- Activates antibody dependent cellular activity
- Triggers mast cell degranulation
- Activates complement
Describe IgG
- Most common type
- Transferred to placenta from mother to baby
Describe IgM
- First type of antibody to be secreted in response to a new antigen
- causes antigen clumping and activating complement
Describe IgA
- Crosses epithelial cells
- Protects epithelial surfaces and present in breast milk
- Secretions (mucous)
Describe IgE
- Fights parasites
- Eosinophils have receptors for IgE
- Release Histamine which damages parasites
Describe IgD
- Role unknown
What are types of humoral immunity?
- Active: B cells are activated -> helps long term
- Naturally acquired: exposed to pathogen
- Artificially acquired: vaccination with
antigen - Passive: obtain antibodies but not activating B cells -> helps short term
- Naturally acquired: breast milk or
antibodies crossing placenta
- Artificially acquired: Vaccine with
antibodies
Describe a Helper T cell
- CD4 positive
- binds to MHC class II
- releases cytokines
- Activates T and B cells
Describe a cytotoxic T cell
- CD8 positive
- binds to MHC class I
- Kills infected or cancerous cells
Where are MHC class II located and what types of antigens do they present?
- Dendritic Cells
- Macrophages
- B cells
- Present exogenous antigen (brought from exterior, processed and presented on exterior)
Where are MHC class I located and what types of antigens do they present?
- Located on all nucleated cells
- Present endogenous antigen (antigen produced internally by host cell after infection and presented on exterior)
What are the different blood types and what do they contain?
- Type A (anti-B antibodies)
- Type B (anti-A antibodies)
- Type AB (neither antibodies)
(universal acceptor) - Type O (both anti-A and anti-B antibodies) (universal donor)
What happens if you give a Type B individual Type A blood?
- Agglutination occurs which is clumping of RBCs and hemolysis occurs due to the anti-A antibodies attacking the newly infused Type A blood
Describe Rh blood groups
Rh blood groups help determine if you have the D antigen, if you are Rh negative, this does not necessarily mean you have anti-D antibodies
What happens when a mother who is Rh “-ve” is exposed to Rh “+ve” fetal RBCs?
- The mother’s immune system will activate B cells producing Anti-D antibodies to attack the Rh “+ve” cells.
- Upon second pregnancy, if the fetus has the same Rh “+ve” RBCs, the new born will have hemolytic disease resulting in anemia, jaundice, enlarged liver and spleen and severe edema.
How do you prevent hemolytic disease of a newborn?
- During and following primary pregnancy, inject anti-D antigen antibodies to remove and fetal RBCs in mother’s bloodstream before an immune response can be triggered
- thus B cells are not activated and no immunological memory of D antigen is acquired
