module 12

Overall goal of the adaptive immune system

To respond to foreign microbes that have breached the external and internal innate defense mechanisms.

Four principles of adaptive immunity: Diversity

Able to respond to an almost infinite number of antigens.

Four principles of adaptive immunity: Specificity

Specific to a target antigen.

Four principles of adaptive immunity: Memory

Remembers and recognizes antigens if they enter again.

Four principles of adaptive immunity: Differentiation

Distinguishes 'self' from 'non-self'.

Cell types associated with humoral immunity

B cells and Helper T (TH) cells.

Goals of humoral immunity

Eliminates extracellular antigens and triggers production of specific antibodies.

MHC class I molecules

Present endogenous antigens and are produced by all nucleated cells.

MHC class II molecules

Present exogenous antigens and are produced by antigen-presenting cells like dendritic cells, B cells, and macrophages.

Humoral response if a helper T cell recognizes the antigen presented on the B cell

Activates B lymphocytes to produce antibodies.

Humoral response if a helper T cell doesn’t recognize the antigen presented on the B cell

No activation of B cells; humoral response is not triggered.

Clonal selection theory

Binding to specific antigen 'selects' a B cell for clonal expansion.

Two main parts of an antibody

The Fab fragment (responsible for antigen binding) and the Fc fragment.

IgM

First class produced during primary response, plays a primary role in bloodstream infections.

IgG

Most abundant class in blood and tissue fluids, provides long-term protection, and can cross the placenta.

IgA

Most abundant class produced overall, provides mucosal immunity against toxins and microbes.

IgD

Involved in the development and maturation of antibody response.

IgE

Responsible for allergic reactions.

Viral inhibition outcome of antibodies

Antibodies attach to surfaces of viruses, preventing attachment to host cells.

Agglutination outcome of antibodies

Antibodies bind antigens on cell surfaces, restricting movement of cells.

Precipitation outcome of antibodies

Antibodies cause soluble antigens to precipitate.

Neutralization outcome of antibodies

Antitoxins bind to toxin molecules to neutralize them.

Opsonization outcome of antibodies

Enhances phagocytosis by marking pathogens for destruction.

Complement activation outcome of antibodies

Bound antibodies activate complement, leading to bacterial lysis.

Primary immune response

First encounter with an antigen taking 10-14 days for antibody accumulation; person may get sick.

Secondary immune response

Faster and more effective than primary due to memory B cells, higher antibody numbers, and often prevents illness.

Cell types in cell-mediated immune response

Cytotoxic T cells and Helper T cells.

Goals of cell-mediated immune response

Targets antigens residing within host cells, including tumor and virally infected cells.

Activation process for T cells

TC cells recognize antigens presented on MHC class I molecules and induce apoptosis via cytotoxic mechanisms.

Process of immunization

Induces immunity by producing memory B cells.

Natural active immunity example

Infection; contact with pathogen.

Natural passive immunity example

Antibodies from mother to fetus via placenta or through milk.

Artificial active immunity example

Vaccination using dead or attenuated pathogens.

Artificial passive immunity example

Administration of exogenous antibodies (gamma globulin).

Three goals of vaccination

Production of memory B cells, high antibody titers, and protection of individual and population (herd immunity).

Herd immunity

A significant portion of the population is immune, preventing disease spread.

Requirements for an ideal vaccine

Should be safe, effective, and stable.

Importance of childhood vaccination

Prevents illness and deaths from vaccine-preventable diseases.

Attenuated vaccine

Live, weakened version of an organism that induces a strong immune response.

Inactivated vaccine

Dead version of an organism that elicits immune response without disease.

Composition of toxoid vaccines

Toxins treated to destroy toxicity but retain antigen.

Composition of subunit vaccines

Key protein antigens or antigenic fragments from pathogens.

mRNA vaccine

Uses mRNA to program cells to create viral antigens and mount an immune response.