CH1 - Intro to the immune system Flashcards
What is the function of the immune system?
Protect individuals against infections and cancer
What is innate immunity?
- early line of defence
- mediated by cells and microbes that are always present and ready to eliminate
What are lymphocytes?
- cells of adaptive immunity
- only cells which clonally distribute receptors specific for different antigens
What is humoral immunity?
antibodies neutralise and eradicate extracellular microbes and toxins
What is cell-mediated immunity?
T lymphs eradicate intracellular microbes
What is adaptive immunnity?
- humoral and cell-mediated Phases: - antigen recog by lymphs - activation of lymphs to proliferate (rapid increase) and differentiate into effector and memory cells - elimination of microbes - decline of immune response - long-lived memory
Which type of cells are the only cells to produce antibodies?
B lymphocytes
- they express membrane antibodies that recognise antigens
What are the descendants of activated B cells?
Plasma cells
What do plasma cells do?
secrete antibodies neutralising and eliminating the antigen
What do T lymphocytes do?
recognise peptide (building blocks of protiens) fragments of protein antigens displayed on other cells
What do helper T lymphocytes do?
produce cytokines that activate phagocytes to destroy ingested microbes, recruit leukocytes and activate B lymphs to produce antibodies
What do cytotoxic T lymphocytes (CTLs) do?
- kill infected cells harbouring microbes in the cytoplasm
What do Antigen Presenting Cells (APC) do?
capture antigens of microbes that enter through epithelia, concentrate them in lymphoid organs and display these antigens for recognition by T cells
Where are lymphocytes and APCs organised?
in peripheral (2ndary) lymphnoid organs
Where are immune responses initated and developed?
Secondary lymphoid organs such as
- lymph nodes (LNs) - spleen - Peyer's patches (PPs) and mucosal tissues- the nasal associated lymphoid tissue (NALT), adenoids, and tonsils.
Where do naïve lymphocytes circulate?
peripheral lymphoid organs –> to search for foreign antigens
What is the role of effector t lymphocytes?
eliminate infectious microbes at peripheral (near surface) sites of infection
What is the role of plasma cells and where are they located?
Secrete antibodies that enter circulation, finding and eliminating microbes
They remain in lymphoid organs and bone marrow
Q - What are the two types of adaptive immunity, and what types of microbes do these adaptive immune responses combat?
Humoral and cell mediated
Humoral: extracellular microbes and toxins
Cell Mediated: intracellular microbes
Q - What are the principal classes of lymphocytes, and how do they differ in function?
T and B cells
T cells: mediators of cell-mediated immunity
B cells: mediators of humoral immunity
Q - What are the important differences among naïve, effector and memory T and B lymphocytes?
Naive cells are mature T or B cells that have not been activated by an microbe antigen yet. They pass through the circulation in lymph nodes or wait in the tissue for a breach.
Effector cells have been activated in some way by the presence of a pathogen. These cells elicit an antimicrobial defense to protect or eliminate pathogens. Most effector cells die after some time, but some live on.
B cells - secrete antibodies that bind to antigens, or initiate the complement system,
T cells - recognize, ingest and destroy microbes, display their peptides to B cells activating their humoral response
Memory B cells live on after the immune response dies down. They can change isotopes of antibody immunoglobulin to improve affinity and specialize for particular antigens. Improve reaction to second exposure.
Where are T and B lymphocytes located in the lymph nodes and how is their anatomic separation maintained?
B: mature in bone marrow
T: mature in thymus
T and B cells initially enter the same region of a lymph node but are then attracted by different chemokines to separate regions of the node
How do naïve and effector T lymphocytes differ in their patterns of migration?
- Naive LCs circulate through the peripheral lymphoid organs searching for foreighn antigens. - Effector T-LCs migrate to peripheral sites of infection and eliminate infectious microbes.
