Immunology overview Flashcards
The immune system
very complex group of many molecules, cells, tissues and organs that provide protection
What does the immune system provide protection from?
Microbes
- Bacteria
- Viruses
- Protozoa
- Helminths
- Fungi
Tumour cells
Foreign material
What are antigens?
Any substance that when recognised by the immune system, will trigger an immune response
- Often can only be recognised by the immune system if presented on the surface of an antigen presenting cell
Features of an APC
apc
antigen
Major histocampatibility complex (MHC) or human leukocyte antigen (HLA) complex
Antibody
AKA immunoglobulin
A specific protein made in response to an antigen
Produced by B cells
What cell is involved in the immune system but also give rise to RBCs & platelets?
Common myeloid progenitor
What cell can also be of lymphoid origin?
Dendritic cell
What are neutrophils?
Rapidly enter infected tissues in large numbers and:
- Release toxic chemicals
- Release chemicals to attract other immune cells (cytokines)
- Phagocytose organisms
- Create neutrophil extracellular traps (NETs)
Use useful in bacterial/ fungal infections
Form pus
What are Basophils? What are Mast cells?
Basophils= Found circulating in the blood
Mast= tissue
- Both release histamine (a vasodilator)
- This helps in the defence against multicellular parasites (e.g. helminths)
- Can cause tissue damage in allergy
What happens if theres too much histamine?
- Too much vasodilation
- Too low blood pressure
- Anaphylaxis
What are eosinophils?
- Contain red granules containing toxic proteins and free radicals
- These help in the defence against multicellular parasites (e.g. helminths)
- Can cause tissue damage in allergy (esp asthma)
Dendritic cells
- Located in tissues that are common points for initial infection e.g. skin, lungs, GI tract
- Main role is as an antigen presentation cell (APC)
Migrate to lymph nodes—- antigen present to other cells—- activation of specific immune response
What are monocytes? What are Macrophages?
Monocytes= found circulating in the blood
Macrophages= found in tissues
- Phagocytosis of debris/ dying cells/ microbes
- APC
Migrate to lymph nodes—– antigen present to other cells—- activation of specific immune response
- Recruit other immune cells (cytokines)
What are Natural killer cells?
- Release perforins and granzymes
- Trigger apoptosis in infected host cells (do not attack pathogen directly
- Trigger apoptosis in cancerous cells
What are (small) lymphocytes?
T- lymphocyte (T cell)
B- lymphocyte (B cell)
Plasma cells
- A specialised type of B cell
- Makes antibodies
What is primary lymphoid tissue?
Where lymphocytes develop and mature
- Bone marrow
- Thymus gland
What is secondary lymphoid tissue?
Where lymphocytes encounter antigens/ pathogens
- Lymph nodes
- Spleen
- Aggregates of lymphocytes at other sites e.g. tonsils, adenoids, Peyer’s patches
What is bone marrow?
Found in the centre of large bones
Site of production of all
- WBCs
- RBCs
- Platelets
Also site of B cell maturation
What is the thymus?
- Site of T cell maturation (produced in bone marrow first)
- Gland behind sternum
- Larger in children, small and fatty in adults
What are lymph nodes?
- Found throughout the body, with large numbers in neck, axilla, groin and paraoritc area etc
- Connected via channel of lymphatic vessels
- Act as areas to “filter out” any infection or cancer cells from the lymph fluid
- APCs in lymph fluid can meet many naive B & T cells in a lymph node
Spleen
Organ in left upper outer quadrant of abdomen
Two tissues admixed
- White pulp (lymphocytes stimulated by antigens)
- Red pulp (filters out old red blood cells)
Types of immunity
Innate vs Adaptive/ acquired
Humoral vs Cell mediated
Passive vs active
Innate vs Adaptive
Innate:
- First line
- Rapid
- Short lasting
- Non- specific
Adaptive/ acquired
- Second line
- Slow
- Long lasting
- Specific (to the antigen)
The innate triggers the adaptive system by presenting antigens
Innate immunity- mechanical & physical barriers
- Intact skin & mucous membranes
- Mucus and cilia
- Tears and eyelashes
- Sweat and body hair
Innate immunity- chemical mediators
- Lysozyme (Cleaves bacterial cell wall)
- Interferon (induces antiviral defences in uninfected cells)
- Complement (lyses microbes/ facilitates phagocytosis)
Innate immunity- immune cells
Phagocytes
- Macrophages
- Neutrophils
Natural killer (NK) cells (Trigger apoptosis of infected cells)
Innate immunity- other
- Competition by normal bacterial flora
- Stomach acid pH
Fever (inhibits pathogen growth)
Adaptive immunity what does it include?
- B lymphocytes (and the specific antibodies they produce)- humoral immunity
- T lymphocytes- cell mediated immunity
Passive immunity
You receive antibodies somebody else has made
- Naturally (e.g. mother to foetus)
- Artificially (pep)
Short term protection
Active
You make your own antibodies/ mount your own immune response
Long term protection
