Immunology: Antibodies, T Cells, Vaccines & Herd Immunity

Adaptive Immune Response

- Properties of immunoglobulin

- IgG (2 binding sites) "Y" shaped molecule

- 80% of total > 2 years old

- Most Ig circulation

- Can cross placenta

- Interacts with complement to aid in phagocytosis (opsonization)

- Neutralize toxins

- Prevent adherence of viruses and microorganisms to host cells

- produced AFTER antigen exposure

- 5 - 10% of circulating immunoglobulins

- Structure in blood is pentamer of 5 subunits = 10 antigen binding sites

- 5 times larger than IgG

- Osponizing antibody that increases phagocytosis

- Most efficient antibody in interacting with complement to aid in phagocytosis & very efficient in agglutination

- Some cases only class of antibody produced against some. Antigens

IgA

- Accounts for about 10 - 13% antibodies, only small proportion are circulating

- Associate with mucous membranes, saliva, and breast milk

- Structurally appear as dimers

- Secetory component transports molecule onto surface of mucous membranes and protects it from destruction by proteolytic enzymes

- Antibodies bind to microorganisms and prevents attachment and colonization

- Secetory IgA in breast milk protects against intestinal pathogens

IgD

- "Y" shaped molecule

- Accounts for <1% of circulating immunoglobulins

- Similar in structure to IgG

- functions during the development and maturation of the antibody response

- Found mostly on surface of B lymphocytes

- Function not clearly defined

IgE

- Y shaped

- BARELY detectable in blood

- Responsible for allergic or hypersensitivity reactions

- IgE is bound to basophiles and mast cells where it causes the release if potential chemicals from auto plastic granules when bound to specific antigen

Development of antibody response

- B - lymphocytes recognize antigens and begin proliferation

- some differentiate into plasma cells

- some differentiate into memory cells that respond the next time that same antigen is presented

- immune specificity permits millions of different antigens to be recognized

Cell-mediated immune response Thymocyte - (T-Cell)

Cell mediated immunity involves T-cells that kill antigen bearing target cells such as virus-infected cells, cancer cells, and tissue/organ grafts or transplants. T-cell system has developed to eliminate these altered self-cells, which pose threat to normal functioning of body

- Immunologic tolerance denotes specific unresponsiveness to antigen

- immune response is carefully controlled by several mechanisms to prevent overproduction of antibody or immune T-lymphocytes

- T suppressor cells

- CD3 +

T - helper cells

CD4+ (marker.expressed on t - helper cells)

- CD8+ (marker.expressed on t- cytotoxic cells)

- Artie of CD4+ and CD8+ t-cells in normal human peripheral blood is approximately 2:1, but may be altered by immunodeficient disease, autoimmune diseases, and others

Autoimmune disease

- normally immune system makes proteins called antibodies that protect from invaders. Autoimmune mean the immune system cannot tell the difference between these invaders and the healthy tissues, this creates autoantibodies that attack and destroy healthy tissue. These autoantibodies cause inflammation, pain, and damage in various parts of body.

Vaccination and Immunization

- immunity can be natural or artificial and active or passive

- artificial immunity is active by administration of vaccine

- live attenuated - viable, but unable to cause disease

- inactivated immunizing agents - killed bacteria, viruses or inactivated toxins

- subunit vaccines

Killed vaccines

- infectious agent unable to replicate in host

- consistent either of whole organisms that have been treated with heat or chemicals to inactivate them or specific components or extracts of pathogens

Advantages of killed vaccines

- cannot revert to pathogenicity and therefore cannot cause infectious disease in host

- will not harm immune suppresses individuals

Disadvantages of killed vaccines

- less likely to elicit a cell=mediated immune response

- multiple boosters may be required

- can still induce side effects, cause by allergic reactions to vaccine components or by toxic contaminants in vaccine preparations

Live vaccines

- consist of attenuated forms of pathogenic viruses or bacteria that are still able to replicate in recipient but are unable to cause disease

- traditionally made by growing the pathogenic viruses in culture in sub-optimal conditions

- this select for viruses that have undergone mutations which adapt them to the new conditions and make the less able to grow in their original host

Advantages of live, attenuated vaccines

- an infect host cells and induce cell-mediated immunity as well as humoral immunity

- because they grow within host, an effective immune response may require fewer immunizations and the resulting response may be longer lasting

- vaccinated individuals can infect individuals and thus spread immunity within the population

Disadvantages of live, attenuated vaccines

- may revert to wild-type

- cannot be given to immune suppressed individuals

- must be grown in cells in tissue culture - creates possibility of contamination with other pathogens

- may induce severe side effects in some individuals

MRNA vaccines

- trigger an immune response, many vaccines put a weakened or inactivated germ in bodies. Not mRNA c vaccines, instead use mRNA create do lab to teach cells how to make a protein that triggers an immune response inside bodies, which produced antibodies, protects us from getting infected if renal virus enter bodies

Herd Immunity

- Not ALL individuals will develop protective immunity

- If majority are immune, non-immune are still relatively protected from infection as the spread of the pathogen through the pop. Will be impaired

- Mandatory vaccination generally results in high levels of herd immunity

High herd immunity

Majority of pop. Is immune to an infectious agent and it is difficult for pathogen to spread

Low heard immunity

Easy for pathogen to spread through pop.