Immune System - Lecture 2 Part B Flashcards
What is Phagocytosis?
The process of ingesting and destroying a pathogen
What are the main cells that perform Phagocytosis?
- Monocytes
- Macrophages
- Neutrophils
- Dendritic cells
What are the two main ways that Phagocytosis can be stimulated?
- Phagocytes recognizes PAMPs from a pathogen
* Phagocyte has receptors for opsonized pathogens
Which complement protein is an example of an Opsonin?
C3B
What can function as Opsonins?
C3B
What is the difference between Opsonin and PAMP activated Phagocytosis?
Opsonized pathogens have an enhanced internalization
What is Phagocytosis used for besides being used to kill?
To clean the a site post-infection
What do Phagocytes use to recognize a pathogen?
PAMPs or Opsonins
What happens after a Phagocyte recognizes PAMPs or Opsonins?
The membrane of the phagocyte starts elongating and surrounding the microbe for the process of internalization forming a phagosome
What occurs in Phagocytosis once a Phagosome is formed?
The phagosome fuses with lysosome forming a phagolysosome which destroys the pathogen
What steps must be taken if a pathogen was phagocytized by an antigen presenting cell?
The phagocyte must present the antigen to T lymphocytes for adaptive immunity
What does the processing of Antigen presentation on a phagocyte depend on?
Whether it is an intracellular or extracellular antigen
What is the process for presenting extracellular antigens?
After being ingested in the cell, the cell produces MHC II which fuses with an endosome of phagolysosome which degrades the invariant chain and exposes the binding site to the foreign antigen which binds to it and then migrates to the surface of the cell
What does the Invariant chain on an MHC molecule do?
Prevents it from binding to our own proteins
What do antigens presented by MHC II molecules get recognized by?
CD4+ lymphocytes or T-helper cells, T-lymphocytes
Once an antigen is presented by MHC II what can it go on to do?
Activate T lymphocytes
What is the process for antigen presenting of intracellular pathogens?
The virus is already in the cell and during replication a viral coating will be released into the cytoplasm and is destroyed by the protease system. The foreign peptides created from this go to the endoplasmic reticulum where MHC I molecules are produced and bind to antigens to express it on the plasma membrane
What are intracellular antigens expressed by?
MHC I
What are extracellular antigens expressed by?
MHC II
What are antigens presented by MHC I recognized by?
CD8+ lymphocytes or T-cytotoxic lymphocytes
What does MHC stand for?
Major histocompatibility complex
Which molecules present intracellular antigens?
MHC I molecules
Which type of MHC molecules are responsible for regular surveillance of the cells and why?
MHC I because they are present in all nucleated cells
How does MHC I act as a window to what is happening inside the cell?
An infected or tumor cell has reduced MHC I expression
Which cells are the best to eliminate infected MHC I cells?
T-cytotoxic cells
What cells are required for T-lymphocyte activation?
MHC II cells presenting antigens
Which cells are the best for fighting extracellular antigens presented by MHC II?
CD4+ lymphocytes and helper-T cells
How do we prevent an exacerbated reaction in adaptive immunity?
By requiring antigen presenting cells to activate T-lymphocytes
How does the Complement system stimulate the adaptive immune response?
By stimulating phagocytosis through opsonins and by stimulating inflammation
