Pathophysiological Concept Chapter 7: Adaptive Immunity

Adaptive Immunity Overview

• Adaptive immunity, also known as the immune response, involves lymphocytes and antibodies.
• Response time is slower compared to inflammation, taking 7 to 14 days to activate.
• It is a specific response, tailored to the unique characteristics of the infecting microbe.
• The adaptive immune system retains memory, enabling quicker responses upon reinfection.

Key Components

• Antigens: Molecular targets that antibodies and lymphocytes respond to.
• T Lymphocytes (T cells): Develop in the thymus; perform functions like identifying and killing targets, regulating, or suppressing immune responses.
• B Lymphocytes (B cells): Develop in bone marrow; mature into plasma cells, which produce antibodies.
• Memory Cells: Formed from both T and B cells; they are activated rapidly during subsequent infections.

Immunity Types

• Humoral Immunity: Involves antibodies that circulate in the blood to combat extracellular microbes and toxins.
• Cellular Immunity: T cells travel through blood and tissues to defend against intracellular pathogens like viruses.
• Active (Acquired) Immunity: Developed in response to antigens, resulting in the production of antibodies due to infections or vaccinations.
• Passive (Acquired) Immunity: Occurs from exposure to infectious agents without pre-existing immunity; includes maternal antibodies transferred to newborns via placenta or breast milk.

Immunoglobulins (Antibodies)

• Immunoglobulin is the general term, while antibody refers specifically to the immune proteins.
• There are five classes of immunoglobulins:
  • IgG: Most prevalent in blood; protective and can cross the placenta, safeguarding newborns for the first six months.
  • IgA: Present in blood and secretions, playing a key role in mucosal immunity.
  • IgM: The largest antibody; first to respond during initial antigen exposure.
  • IgE: Involved in allergic reactions and defense against parasites.
  • IgD: Functions as an antigen receptor on early B cells.

Secretory (Mucosal) Immune System

• Comprises lymphoid tissues that protect the body's external surfaces.
• Antibodies are found in tears, sweat, saliva, mucus, and breast milk, with IgA being the dominant type in these secretions.

Pediatric Immunity

• Infants have sufficient levels of immunoglobulin M (IgM) but show deficiencies in immunoglobulin G (IgG) and immunoglobulin A (IgA) responses.
• Maternal antibodies transfer to the fetus, providing critical immunity during fetal circulation and for the first few months after birth.

Geriatric Immunity

• Aging leads to decreased T-cell activity; the thymus shrinks to about 15% of its maximum size, affecting immune function.
• Thymic hormone production declines, impairing the organ’s capacity for T-cell differentiation.
• Older adults exhibit a reduced antibody response to antigens, compromising their ability to fight infections effectively.

Pediatric Immunity

• Infants have sufficient levels of immunoglobulin M (IgM) but show deficiencies in immunoglobulin G (IgG) and immunoglobulin A (IgA) responses.
• Maternal antibodies transfer to the fetus, providing critical immunity during fetal circulation and for the first few months after birth.

Geriatric Immunity

• Aging leads to decreased T-cell activity; the thymus shrinks to about 15% of its maximum size, affecting immune function.
• Thymic hormone production declines, impairing the organ’s capacity for T-cell differentiation.
• Older adults exhibit a reduced antibody response to antigens, compromising their ability to fight infections effectively.

Pediatric Immunity

• Infants have sufficient levels of immunoglobulin M (IgM) but show deficiencies in immunoglobulin G (IgG) and immunoglobulin A (IgA) responses.
• Maternal antibodies transfer to the fetus, providing critical immunity during fetal circulation and for the first few months after birth.

Geriatric Immunity

• Aging leads to decreased T-cell activity; the thymus shrinks to about 15% of its maximum size, affecting immune function.
• Thymic hormone production declines, impairing the organ’s capacity for T-cell differentiation.
• Older adults exhibit a reduced antibody response to antigens, compromising their ability to fight infections effectively.

This quiz covers the essentials of adaptive immunity, including its components, response mechanisms, and types. Learn about lymphocytes, antibodies, and the significance of memory in immune responses against infections. Test your understanding of how the adaptive immune system operates in response to pathogens.