BMSC207 Lecture Notes - Lecture 15: Mannose, T Cell, Epitope
Immune mechanism (overview):
Innate Response Mechanisms:
Innate immune response is the first line of defence:•
Barriers○
Phagocytes○
Inflammation○
Complement
○
Includes:•
Barrier defence:
Anatomical barriers include physi cal, chemical and biological barriers•
Includes skin, cilia, mucous membranes •
Phagocytes:
large leukocytes found in tissues that has phagocytic and antigen-presenting capaci ties○
Macrophage:•
Active mobile granulocytes○
Neutrophils:•
Precursors of macrophages, they are large cells found in tissues such as lymph○
nodes and spleen
Monocytes:•
function in phagocytosi s and antigen presentation, when they ingest antigen,○
they move to the lymph node to present antigen to T cell
Dendritic cells:•
The activation of certain genes in phagocytes enhances their phagocytic and pathogen-•
Phagocytic cells use toxic oxygen to kill ingested bacteria cells by oxidizing key○
cellular constituents
Occurs within the phagocytic cell, which is not damaged by the toxic oxygen product○
killing abilities
Membrane bound phagocyte proteins that recognize pathogen-associated ○
molecula r patterns (PAMPs), toll-like receptors (TLRs) recognize PAMPs
Recognize things that are only found on pathogens, and not host cells (such as ○
flagell in, bacterial lipoproteins etc.)
Phagocytes recognize a pathogen usi ng pattern recognition receptors(PRRs)
•
Inflammation:
Redness, swelling, pain, and heat localized at site of infection○
Inflammation is a nonspecific reaction to noxious stimuli•
Effective inflammatory response isolates and limits tissue damage, destroying damaged cells
pathogens
○
Inflammation can result in considerable damage to healthy tissue○
Molecular mediators of inflammation are proteins called cytokines and chemokines•
Complement:
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Lecture 8
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19/9/16
Monday, 19 September 2016
6:07 PM
Lectures Page 1
Complement is composed of a group of sequentially interacting proteins•
Cause lysis of pathogens or mark them for recognition by phagocytes○
Individual proteins of complement are called C1, C2, C3, etc. (don't need to know all of these)○
These proteins react in a defined sequence - defined as a cascade○
Complement lyses many gram-negative bacteria○
Important roles in innate and adaptive immunity•
Membrane-bound components of complement (membrane attack components, or MAC) insert in
membrane to form a pore
•
A bacterial cell is more likely to be phagocytized if it has been bound to an antibody•
Binding of complement further enhances phagocytosis○
Enhancement of phagocytosis by antibody or complement binding is called opsonisation
○
Complement activation can also be achieved by the mannose-binding lectin pathway and the
alternative pathway
•
Mannose -binding lectin
Although the innate immune response is good, sometimes it is not good enough•
Staphylococcus aureus and Mycobacterium tuberculosis○
Some pathogens have developed mechanisms for neutralizing toxic phagocytic products•
Streptococcus pyogenes and S. Aureus○
Some intracellular pathogens produce leukoci dins that kill the phagocyte•
Streptococcus pneumoniae ○
Some bacteria produce a capsule resistant to phagocytosis•
The acquired immune system:
Considering the amount of bacteria we come in contact with on a day to day basis, sometimes the
innate immune system is not enough, which is when we call on the acquired immune system
•
The acquired immune response has 2 main parts, the humoral immunity and cell-mediated immunity•
B-cell antibody based○
Good at clearing extracellular organisms and pathogens○
Humoral immunity:•
T-cell based○
Important for any intracell ular organi sm and pathogens (viruses)○
Cell-mediated immunity:•
Both work on different aspects of infection but also work together•
Adaptive response properties:
In cell-mediated immunity, pathogen-infected host cell s are killed after they are recognized via
pathogen antigens found on their surface
○
Antibody-mediated immunity is effective against extracellular pathogens such as bacteria and
soluble pathogen product
○
T lymphocytes recognize the peptide antigens through cell surface T cell receptors (TCRs)•
of antigen–antibody reaction is dependent on lymphocyte cell receptors interacting with
individual pathogen
○
Pathogen specific - innate is general
○
Specificity:
•
Subsequent exposures to the same antigen result in rapid production of large quantities of
reactive T cells or antibodies
○
Memory:
•
The acquired inability to make an adaptive immune response to one's own antigens○
Discrimination between foreign and host antigens○
Stops us from killing ourselves○
Usually happens between the ages of 0-3 years old○
Tolerance:
•
Respondi ng cells
Immunogens and Antigens:
Antigens (toxins or bad things that need to be rid of) are substances that react with antibodies or TCRs (T
receptors)
•
Immune system sees them, but doesn't trigger an immune response
Haptens are not immunogens, although they are antigens○
Will trigger an immune response
Complex proteins and carbohydrates are immunogens○
Not all antigens are immunogens (substances that induce an immune response)•
Lectures Page 2
Document Summary
Innate immune response is the first line of defence: Anatomical barriers include physi cal, chemical and biological barriers. Macrophage: large leukocytes found in tissues that has phagocytic and antigen-presenting capacities. Precursors of macrophages, they are large cells found in tissues such as lymph nodes and spleen. Dendritic cells: function in phagocytosi s and antigen presentation, when they ingest antigen, they move to the lymph node to present antigen to t cell. The activation of certain genes in phagocytes enhances their phagocytic and pathogen- killing abilities. Phagocytic cells use toxic oxygen to kill ingested bacteria cells by oxidizing key cellul ar constituents. Occurs within the phagocytic cell, which is not damaged by the toxic oxygen product. Phagocytes recognize a pathogen usi ng pattern recognition receptors(prrs) Membrane bound phagocyte proteins that recognize pathogen-associated molecular patterns (pamps), toll-l ike receptors (tlrs) recognize pamps. Recognize things that are only found on pathogens, and not host cells (such as flagellin, bacterial lipoproteins etc. )
