Immune System 3 Part 2 Flashcards
What does it mean by Exogenous Antigen? How do these Antigens enter the immune cell?
“exogenous antigen” refers to antigens that come from outside the body, such as those derived from pathogens like bacteria or viruses.
enters by phagocytosis
Antigen Presentation Steps
What 4 steps are involved in an Exogenous Antigen entering a cell?
- Phagocyte recognizes and ingests antigen by phagocytosis.
- Antigen broken down and a piece combined with MHC class II.
- Vesicle moves the resulting complex to cell surface.
- Exocytosis and insertion of complex on cell membrane surface. (antigen presentation)
Which T Cell can bind the antigen presentation of Exogenous Antigens?
Helper T cell with correct T cell receptor can bind the antigen presentation (clonal selection).
What are the key antigen-presenting cells (APCs) involved in presenting exogenous antigens to helper T cells?
Macrophages and B cells.
What is an Endogenous Antigen?
antigen already inside body cell
What 4 Steps are involved in Antigen Presentation of an Endogenous antigen?
- Intracellular viral protein acts as antigen.
- The Viral protein is broken down and a piece is combined with MHC class I.
- A Vesicle moves the resulting complex to the cell’s surface.
- Exocytosis and insertion of vesicle on cell membrane surface. (antigen presentation)
Which T Cell can bind the antigen presentation of Endogenous Antigens?
Cytotoxic T cell with correct T cell receptor can bind the antigen presentation (clonal selection).
Which MHC Class do most body cells have for Endogenous Antigen Presentation to Cytostoxic T Cells?
Most body cells (except red blood cells) have MHC class I for endogenous antigen presentation to cytotoxic T cells.
After recognition gives us clonal selection, what occurs in the Activation Stage?
Define 2 Terms
Activation gives multiple rounds of clonal expansion (proliferation – increasing clonal numbers / differentiation –increasing clonal specialization)
All clones formed (whether proliferated or differentiated) able to recognize specific antigen from initial clonal selection
What do the Clones Ultimately Form?
2
- Effector cells – carry out immune attack.
- Memory cells – not active in attack; stored for future encounters with same specific antigen
What characterizes the “Attack Stage” in the immune response, and what are the two main types of attack mechanisms?
The Attack Stage involves two main types of mechanisms:
- Cell-mediated (no antibodies): Targets intracellular pathogens and cancer cells.
- Antibody-mediated (involves antibodies): Targets extracellular pathogens.
Describe the process of Full Helper T cell Activation during the immune response, focusing on the steps following clonal selection:
3
Following clonal selection, Helper T cell activation involves:
- Antigen presentation (clonal selection).
- Costimulation (nonantigen binding) to fully activate
- Secretion of cytokines after full Activation (e.g., interleukin 1 (IL-1) / tumor necrosis factor alpha (TNF-α)).
Once the Helper T cell is fully activated, what does it Secrete and what does it Stimulate?
3
The final steps of Helper T cell activation include:
1. Secretion of interleukin 2 (IL-2) by the fully activated Helper T cell.
2. Stimulation of full clonal expansion, resulting in effector and memory cells.
3. Effector cells release more IL-2 and other cytokines.
What actions does the Activated Helper T Cell perform? What does this Trigger?
Activated helper T cell releases IL-2 and interferon type II (interferon gamma).
Trigger macrophages and NK cells to proliferate and become “activated” versions
What can actvated version of macrophages and NK cells do?
Activated versions can secrete cytotoxic chemicals that destroy target cells.
These “activated” macrophages and NK cells are non- specific (innate) binding, but reliance on activated helper T cells makes them part of adaptive immune response.
