Module 12

Host Defense Mechanisms

Host Defense Mechanisms

Ways in which the body protects itself from pathogens.

Nonspecific Host Defense Mechanisms

Ways in which the body attempts to destroy all types of substances that are foreign to it, including pathogens.

First Line of Defense

The initial barrier that pathogens encounter, including intact skin and mucous membranes.

Second Line of Defense

It is the nonspecific line of defense. These are ways in which the body attempts to destroy all types of substances that are foreign to it, including pathogens.

Third Line of Defense

It is very specific line of defense. Special proteins called antibodies are usually produced in the body in response to the presence of foreign substances.

Skin and Mucous Membranes

Physical and mechanical barriers that prevent pathogens from entering the body.

Nonspecific Host Defense Mechanisms

It is also known innate immunity. It keeps pathogens out or kill them regardless of their type.

Intact Skin

The unbroken skin that serves as a physical barrier to pathogens.

Mucous Membranes

Membranes that produce sticky mucus to trap pathogens and contain toxic substances to prevent their proliferation.

Cellular and Chemical Factors

Factors such as dryness, acidity, temperature, and the presence of certain enzymes that inhibit the colonization and growth of pathogens.

Lysozymes

Destroys peptidoglycan which makes the cell more vulnerable to phagocytosis

Lactoferrin

These are proteins that bind to iron and minerals. These are commonly found in milk, saliva, tears, mucus, and bile.

Lactoperoxidase

It produces superoxide radicals which is highly reactive oxygen that is toxic to pathogens.

Respiratory System

The system responsible for trapping and expelling microorganisms from the respiratory tract.

Gastrointestinal System

The system that kills pathogens entering the GI tract through digestive enzymes, acidity, and peristalsis.

Genitourinary System

The system that inhibits colonization of pathogens through the acidity of vaginal fluid and flushes out pathogens during urination.

Microbial Antagonism

When indigenous microbiota prevent the establishment of arriving pathogens.

Transferrin

The main protein in the blood that maintains iron homeostasis.

Sequestration

It means to take away

Interferons

Small, antiviral proteins produced by virus-infected cells that stimulate the immune response.

Acute Phase Proteins

Plasma proteins that increase rapidly in response to infection, inflammation, and tissue injury.

Cytokines

Chemical messengers that regulate the intensity and duration of immune system responses.

Phagocytosis

The process by which phagocytes engulf and destroy foreign material.

Complement

A group of approximately 30 different proteins that are found in the blood plasma. This is also called as cascade.

Opzonization

It is the process by which phagocytosis is facilitated by the deposition of opsonins onto the surface of particles or cells.

Membranous Attack Complex

It is a complex of complement proteins; form a pore across the cell membrane which is a small opening.

Inflammation

It is a complex series of events in which the body responds to any local injury, irritation, microbial invasion, or bacterial toxin.

Fever

It is the first sign of infection

Pyrogens

It is a substance that stimulate the production of fever. It may originate either from outside or inside of the body.

Specific Host Defense Mechanism

It is also called as adaptive immunity. It remembers the pathogens that has invaded the system, then produce a powerful response on the next entry.

Active Natural Immunity

A natural response to an antigen which leads to the development of antibodies.

Active Artificial Immunity

Deliberate introduction of antigen to an individual to induce immune response.

Passive Natural Immunity

It is the transfer of antibodies from mother to child. For instance, the IgG. Colustrum gives newborn antibodies to protect them during the first few months of life.

Passive Artificial Immunity

It is the development of immunity by a third party.

Humoral Immunity

It is also known as antibody-mediated immunity. It always involves the production of antibodies in response to antigens. They remain in blood plasma, lymph, and other body secretions where they protect against the specific pathogens that stimulated their production.

Vaccines

Material that can artificially induce immunity to an infectious disease, usually after injection or, in some cases, ingestion of the material.

Attenuated Vaccine

A type of vaccine made from weakened or modified forms of the disease-causing pathogen. It stimulates an immune response without causing severe illness. It should not be given to immunosuppresed individuals.

Inactivated Vaccine

A type of vaccine that contains killed or inactivated pathogens through heating or using chemicals to stimulate an immune response without causing disease.

Subunit Vaccine

It is also called as acellular vaccine. It uses antigenic portions of a pathogen, rather than using the whole pathogen.

Conjugate Vaccine

It is made by conjugating bacterial capsular antigen to molecules that stimulate immune system to produce antibodies against the less antigenic capsular antigens.

Toxoid Vaccine

They create immunity to the parts of the germ that cause a disease instead of germ itself.

DNA Vaccine

It is also called gene vaccines. They are currently experimental. It works by using a particular gene from a pathogen then it is inserted into plasmids, and the plasmids are then injected into skin or muscle tissue.

Autogenous Vaccine

It is prepared from bacteria isolated from localized infection. The pathogen are killed and then injected to the same person to induce production of more antibodies.