Introduction to the Immune System Flashcards
Functions of the Immune System
- To prevent damage to the host from invading pathogens.
- To learn from the first encounter of the pathogen, and generate memory that allow a faster and stronger response at the next encounter.
- To recognize the difference between foreign and self.
- To avoid and prevent destruction of normal tissues/organs.
Innate
Pre-exsiting
Adaptive
Learned
All blood cells are generated by
Hematopoieses (formation of blood cells from HSCs in bone marrow)
Where do immune cells develop?
Bone Marrow - HSCs gives rise to all types of blood cells and is capable of self-renewal.
What types of main progenitors arise from bone marrow?
- Common Lymphoid Progenitor
- Common Myeloid Progenitor
What is the function of the Common Lymphoid Progenitor?
It leads to the production of immune cells primarily found in the lymphoid tissues and circulating in the blood.
- B Cells
- T Cells
- Natural Killers (NKs) Cells
- Innate Lymphoid Cells (ILCs)
What are the Common Myeloid Progenitors?
Granulocytes/Macrophages Progenitor:
* Granulocyte: Neutrophil, Eosinophil, and Basophil.
* Monocyte
* Immature Dendritic Cell
* Unknown Precursor of Mast Cells
Megakaryocyte/Erythrocyte Progenitor:
* Megakaryocyte
* Erythroblast
What is the function of the effector cells?
They are the functionally active forms of the lymphoid cells after they have been activated on response to pathogens or other immune stimuli, these include:
* Plasma cells (activated B cells) that secrete antibodies.
* Activated T-cells, NK cells, and ILCs that carry out immune responses like targeting infected or cancerous cells.
What are the principles of Innate Immunity?
- First lines of defense include anatomic barriers (skin, mucosa) and chemical barriers (antimicrobial peptides, acidic pH, enzymes).
- Pathogen-Associated Molecular Patterns (PAMPs) initiate immune responses through pattern-recognition receptors (PRRs).
- Innate immune cells are continuously produced in the bone marrow and increase in response to infection.
PAMPs are found on
On the surface of the pathogens like bacteria or viruses but not in the host.
PAMPs have inflammatory inducers that
Activate the immune system, the presence of ATP (release by damaged cells) and urate crystals (associated with cell damage) can also trigger inflammation.
Sensor Cells are immune cells that express PRRs, which can detect PAMPs. Important sensor cella are:
- Macrophages
- Neutrophils
- Dendritic cells
After the sensor cells recognize PAMPs, they release signaling molecules known as mediators:
Cytokines and Cytotoxicity
These are the tissues or areas where the immune response is ultimately directed.
The final goal of the immune response is to eliminate the pathogen and restore homeostasis.
Target Tissues
What are the function of target tissues?
- Production of antimicrobial proteins.
- Induction of intracellular antiviral proteins.
- Killing of infected cells.
What are the MYELOID DERIVED innate immune cells?
- Macrophages
- Eosinophil
- Dendritic Cells (DCs)
- Basophil
- Neutrophil
- Mast Cell
What are the LYMPHOID DERIVED innate immune cells?
Innate Lymphoid cells (ICLs) - ILC1, ILC2, and ILC3.
Natural Killers (NK) cells
What are the temporal differences in innate and adaptive immune responses?
Innate immunity - Hours
Adaptive immunity - Days
Learn Image.
Where do adaptive immune cells develop?
- B cells and T cells precursos on Bone Marrow
- T cells on the Thymus
Tcells are educated in the thymus
Bcells are educated in the bone marrow
Characteristics of B-cells:
- Recognize secondary and tertiary structure
- Learn to ignore self antigens
- Surveil the system looking for foreign antigens/allergens
- Expand antigen specific clones
- Produce antibodies that eliminate pathogens/allergens/cancer through several mechanism.
Characteristics of T-cells:
Recognize peptides bound to MHC.
Learn to ignore self antigens
Surveil the system looking for foreign antigens/allergens
Proliferate and produce effector cytokine, chemokines
Lyse target cells to eliminate pathogens/cancer/reject organs.
Provide help to B-cells and T-cells
Recruit innate immune cells.
Where do adaptive immune cells arise?
After maturation. adaptive immune T and B cells migrate and reside in:
Lymphois Organs (LN, Spleen, Mucosa-associated lymphoid tissues, Bone Marrow).
Circulating in the Blood and Lymphatic System.
Inflamed or Infected Tissues
What are the functions of the Dendritic Cells between the innate and adpative immune responses?
They form the bridge between innate and adpative immune responses.
DCs process antigens that are presented to B and T cells to activate adaptive immune responses
DC subsets are circulating and tissue-resident.
Infection and Vaccination generate…
Mucosal Immunity
Initial pathogen clearance is followed by…
development of immunological memory
Consequences of immune response
Summary
