Chapter 15

Apoptosis Definition

Programmed cell death for infected or damaged cells; characterized by the cell dismantling itself from within without triggering inflammation.

Process of Apoptosis

Includes DNA destruction and 'blebbing', where cells bubble and break into vesicles, later cleared by macrophages.

Fever

Defined as a body temperature above $37.8 \, ^\text{°C}$; normal body temperature is $37 \, ^\text{°C}$.

Role of Pyrogens

Substances that induce fever; in Gram-negative bacteria, the pyrogen is Lipid A, part of the LPS in the outer membrane.

Benefits of Fever

Inhibits pathogen growth and accelerates immune cell activity.

Risks of Fever

Excessively high fevers can cause tissue damage and may require treatment with Tylenol or Advil.

Third Line of Defense

The adaptive response that is highly specific and provides long-term protection, unlike innate immunity.

Primary Response

The immune response that occurs upon the first exposure to a pathogen, taking approximately 10 to 14 days to fully develop.

Secondary Response

The immune response triggered by subsequent exposures to a pathogen, characterized by a rapid and intense response due to immunologic memory.

Mechanism of Memory

Involves memory B cells differentiating into plasma cells that produce large quantities of antibodies to neutralize pathogens before illness occurs.

Humoral Immunity

Targets extracellular pathogens and is mediated by B cells (B lymphocytes) that mature in the bone marrow.

Cell-Mediated Immunity (CMI)

Targets intracellular pathogens and is mediated by T cells (T lymphocytes) that mature in the thymus.

Helper T Cells

Also known as CD4 cells; they are central regulators of both humoral and cell-mediated immunity.

Antigens

Compounds that elicit an immune response; specifically, epitopes are the antigenic determinants on a microbe's surface.

Antibody Structure

Y-shaped proteins (immunoglobulins) consisting of four polypeptide chains.

Fab Region

The variable region of an antibody that contains the antigen-binding site.

Fc Region

The constant region of an antibody that remains the same for a specific class of antibody.

Neutralization

The process of preventing a virus or toxin from binding to host receptors.

Immobilization

The strategy of preventing bacterial adherence.

Cross-linking

The clumping together of multiple bacteria for efficient phagocytosis.

Opsonization

The coating of a pathogen to enhance recognition and uptake by phagocytes.

IgM

A large pentamer; the first antibody produced during a primary response and the only one produced by a fetus in utero.

IgG

The most abundant and long-lasting antibody; crosses the placenta, found in breast milk, and is the primary antibody of the secondary response.

IgA

A dimer found in secretions like mucus, tears, saliva, and breast milk; provides mucosal protection.

IgD

Involved in the maturation of the immune response and B cells.

IgE

Involved in allergic reactions, triggering histamine release from mast cells.

Herd Immunity

Occurs when a high percentage (typically 90-95%) of the population is immune, preventing the spread of disease to susceptible individuals.

Natural Active Immunity

Immunity from an actual infection.

Artificial Active Immunity

Immunity from vaccination.

Natural Passive Immunity

Antibodies passed from mother to child (e.g., via placenta or breast milk).

Artificial Passive Immunity

Injection of antiserum, antitoxin, or antivenom.

Attenuated Vaccines

Live, weakened microbes that provide strong, long-lasting immunity but carry a risk of reverting to pathogenic form or causing disease in the immunocompromised (e.g., MMR, Chickenpox).

Inactivated Vaccines

Dead or inactive agents that cannot cause infection but often require boosters; some use adjuvants (e.g., Fluad) to enhance the response.

Polio Vaccine Switch

The US switched from the oral polio vaccine (OPV) to the inactivated polio vaccine (IPV) in 1995 to eliminate vaccine-acquired cases.

Measles Elimination

Measles was declared eliminated in the US in 2000, but cases have surged due to importation and low vaccination rates.

SB 277 (2016)

This legislative response removed non-medical exemptions for school vaccinations in California.

SB 276 (2019)

This legislation established oversight to prevent fraudulent medical exemptions in California.

$$IgM$$

A large pentamer; the first antibody produced during a primary response and the only one produced by a fetus in utero.

$$IgG$$

The most abundant and long-lasting antibody; it crosses the placenta, is found in breast milk, and is the primary antibody of the secondary response.

$$IgA$$

A dimer found in secretions like mucus, tears, saliva, and breast milk; provides mucosal protection.

$$IgD$$

Involved in the maturation of the immune response and B cells.

$$IgE$$

Involved in allergic reactions, triggering histamine release from mast cells.

Antigens

Compounds that elicit an immune response; specifically, epitopes are the antigenic determinants on a microbe's surface.

Antibody Structure

Y-shaped proteins (immunoglobulins) consisting of four polypeptide chains.

Fab Region

The variable region of an antibody containing the antigen-binding site.

Fc Region

The constant region of an antibody that remains the same for a specific class of antibody.

Neutralization

The process of preventing a virus or toxin from binding to host receptors.

Immobilization

The process of preventing bacterial adherence.

Cross-linking

Clumping multiple bacteria together for efficient phagocytosis.

Opsonization

Coating the pathogen to make it easier for phagocytes to recognize.

Adaptive Immune Response

The highly specific third line of defense that provides long-term protection against pathogens.

Primary Response

The immune response that occurs upon the first exposure to a pathogen, taking approximately 10 to 14 days to develop.

Secondary Response

A rapid and intense immune response triggered by subsequent exposures to a pathogen due to immunologic memory.

Memory B Cells

Cells that differentiate into plasma cells during an immune response, producing large quantities of antibodies to neutralize pathogens.

Humoral Immunity

The aspect of immunity that targets extracellular pathogens, mediated by B cells that mature in the bone marrow.

Cell-Mediated Immunity

The aspect of immunity that targets intracellular pathogens, mediated by T cells that mature in the thymus.

Helper T Cells

CD4 cells that are the central regulators of both humoral and cell-mediated immunity; their destruction compromises the immune system.