Week 2 (Part 2): Adaptive Immunity - Humoral Immunity B-Cells Flashcards
Properties of Adaptive immunity (6):
1) Can distinguish one specific microbe from another
2) Develops memory for subsequent exposures of that same microbe
- Subsequent exposure, can respond faster
3) Two types:
- Humoral Immunity (B Lymphocytes) – production of antibodies
- Cell-mediate immunity (T Lymphocytes) – destroyed invaders
4) T cell immunity important against intracellular pathogens
5) B cell immunity (Abs) help eliminate extracellular pathogens
6) Cannot distinguish microbial antigens from self antigens (→ autoimmune disorders)
What is the main function of humoral immunity?
Main function is to produce specific antibodies to fight against the particular EXTRAcellular pathogens
Humoral Immunity:
- Where do B-cells arise from?
- Where do they mature?
- What happens after maturation?
B cells arise in the fetal liver and from stems cell in the bone marrow
- They mature in the bone marrow
- Once mature they enter the blood circulation where they migrate and are stored in places like the lymphoid tissue: spleen and lymph nodes
How are B-cell activated?
This happens after exposure to an antigen
What are the steps of B-cell activation?
1) The antigen binds to the B lymphocyte surface receptor (immunoglobulin molecule to antigen epitope) (shown by the BCR in this picture, which is also known as Immunoglobulin molecule)
- This activates the B lymphocyte (which occasionally needs assistance from Helper T cells or other stimuli)
2) Next the lymphocytes proliferate to make identical cell clones
- The cloned cells then differentiate to become either antibody producing cells (plasma cells) or memory cells
Describe plasma cell vs. memory cells:
Both are produced by B-cell activation
Plasma cell: Secrete Ig molecules
- Otherwise known as an antibody
- Non-dividung B-cells
- Live for a few days-weeks
- Die via apoptosis
Memory cell: Recognize and respond to subsequent exposures of the same organism that stimulated their formation
- Live for many years
- Secondary immune response
Describe the primary response vs secondary response?
- How do the amounts differ?
Antibody responses generated during the first exposure to an antigen, called primary responses, differ quantitatively and qualitatively from responses to subsequent exposures, called secondary responses
- The amounts of antibody produced in the primary immune response are smaller than the amounts produced in secondary responses.
What are antibodies produced in response to an antigen also known as?
- How many are there?
- What is the shape?
Immunoglobulins (Ig)
- 5
- Shape is a “Y” - 2 arms and 1 stem (i.e. the arms are the antigen binding sites)
Describe IG:
- Abundance?
- Important feature?
- Type of response?
- Main function?
IgG is the most abundant antibody
- it’s most important feature is that it is able to cross the placenta and protect the fetus resulting in PASSIVE immunity for the fetus that generally lasts for 3 months after birth
- It is prominent in the secondary immune response.
- It’s main function is to enter infected tissue via inflammation to neutralize pathogens and enhance phagocytosis
Describe IgA:
- Where is it found?
- Main function?
IgA is found in bodily secretions such as tears, saliva, intestinal mucus, milk, prostatic fluid and other body secretions
Therefore it’s main function is mucosal immunity on surfaces of the gI and respiratory tract that protect against entrance of bacteria
- It also therefore provides passive immunity to a newborn breast feeding as maternal IgA is the most predominant Ab in colostrum and breast milk
Describe IgM:
- Type of response?
- Main function?
IgM is prominent in the primary antibody response
- Main function is to neutralize pathogens
Describe IgE:
IgE participates in immediate hypersensitivity a type of allergic reaction in which a specific allergen, as well as some parasitic infections as it activates mast cells
-Does not function in neutralization or phagocytosis
Describe IgD:
- Bound to?
- Main function?
IgD mostly remain bound to naïve B cells → main function is to act as a B Cell -Receptor (bind antigens)
- It’s Ab function is unknown
What is the role of antibodies?
How do they accomplish this?
Help eliminate extracellular pathogens
1) Neutralization: block pathogen receptors that are used to gain entry into a cells or tissues
- Antibodies block the pathogens receptors that are used to enter and infect their target cells or tissues
2) Phagocytes express surface receptors that bind Abs, called Fc receptors, which triggers phagocytosis
- Phagocytes express surface receptors that bind antibodies, called Fc receptors.
- Pathogen-bound Abs bind Fc receptors, which triggers phagocytosis.
What is the primary immune response reaction?
- First exposure?
What is the secondary immune response reaction?
- Subsequent exposures?
1) Primary Immune Responseis thereactionof theimmunesystem when it contacts an antigen for the first time.
- First exposure to a protein antigen (IgM always secreted first)
- Occurs with natural infection or vaccination
- Generate plasma cells (effector B cells) and memory B cells
2) Secondary Immune Responseis thereactionof theimmunesystem when it contacts an antigen for the second and subsequent times
- Subsequent exposures to the identical protein antigen
= memory response
- More effective (faster) elimination of pathogen
- Better long-term immune protection
