DBMB 711: Week 3 Lecture

What are the main functions of antibodies?

Neutralization, agglutination, removal of antibody-antigen complexes, complement activation, helping NK cells, and activating monocytes/macrophages.

Do antibodies directly kill pathogens?

No, they do not kill anything directly; they primarily mark targets for destruction by other cells.

What is the FAB region of an antibody?

The fragment antigen-binding (FAB) region is where the antigen binding sites are located.

What is the FC region of an antibody?

The fragment crystallizable (FC) region is the "tail" or "bottom part" of the antibody.

Why is the FC region of an antibody important?

Many immune cells, such as mast cells, have Fc receptors that bind to this region, which can trigger cellular responses like histamine release.

What is the primary function of the variable regions on an antibody?

To allow the antibody to recognize and bind to a wide variety of different antigens.

What is the most abundant immunoglobulin in the body and the only one that can cross the placenta?

IgG

Which immunoglobulin is predominantly found on mucosal surfaces?

IgA

What is the structure of IgA when found in mucosal secretions?

It exists as a dimer (two units) held together by a J chain and a secretory component.

What is the origin of the secretory component of secretory IgA (sIgA)?

It is a piece of the Fc receptor from the epithelial cell that transports the IgA dimer across the mucosal barrier.

What is gingival crevicular fluid (GCF)?

It is a fluid found in the subgingival space (gingival crevice) that is more like a blood filtrate than saliva, containing proteins like albumin and predominantly IgG antibodies.

Which antibody is the first to be produced during a primary immune response?

IgM

A high level of IgM against a specific pathogen suggests what stage of infection?

The early stages of an infection.

Which antibody is primarily associated with allergic reactions and parasitic infections by binding to Fc receptors on mast cells?

IgE

What is the primary role of IgD?

It is primarily found as a B cell receptor on the surface of B cells and is not typically secreted as an antibody.

How are the vast number of different antibody specificities generated in the body?

Through random gene rearrangement during B cell development, creating a diverse repertoire of B cells before any antigen is encountered.

What are cytokines?

Small proteins that act as cellular messengers, secreted by immune cells and other cell types to regulate immune responses.

Which three pro-inflammatory cytokines are most important to know for oral inflammatory diseases like periodontitis?

IL-1, IL-6, and IL-8

What is the main function of IL-8?

It is a chemokine that attracts neutrophils to the site of inflammation and can be secreted by macrophages and epithelial cells.

Which cytokine is known for its anti-inflammatory properties, helping to downregulate the immune response?

IL-10

Which pro-inflammatory cytokine is a major player in the pathogenesis of inflammatory diseases like periodontitis and rheumatoid arthritis?

IL-17

What are interferons (IFNs)?

Cytokines that are crucial for antiviral defense; an infected cell releases them to warn neighboring cells to upregulate their antiviral mechanisms.

Which cytokine is primarily involved in wound healing?

Transforming growth factor-beta (TGF-beta)

What are the two main immune strategies in the oral cavity?

Immune exclusion and inflammation.

Define "immune exclusion" in the context of the oral cavity.

The process of inactivating and clumping antigens (like microbes) so they can be swallowed and eliminated from the body.

What are defensins?

Small antimicrobial peptides produced by epithelial cells and various immune cells that contribute to the innate defense in the oral cavity.

How does the oral epithelium act as a physical barrier?

Through keratinization, a basement membrane, and the constant shedding of its top layers (desquamation), which helps remove adherent bacteria.

How can some periodontal pathogens, like P. gingivalis, evade the immune system?

By hiding inside epithelial cells, where they are protected from antibodies.

What is "colonization resistance"?

The process where the normal oral microbiota prevents pathogens from establishing themselves by competing for space and nutrients and by producing antimicrobial substances.

What is the term for a healthy, stable microbial community, such as in the oral cavity?

Eubiosis

What is the term for a disturbed or imbalanced microbial community, which can lead to disease?

Dysbiosis

What often causes dysbiosis in the oral cavity, allowing opportunistic pathogens like Candida to thrive?

Disruption of the normal microbiota, often due to antibiotic therapy.

"Does periodontal disease follow Koch's postulates (one germ, one disease)?"

No, it is typically caused by dysbiosis—an imbalance in the entire bacterial community—rather than a single pathogen.

What are T helper 17 (Th17) cells?

A subset of T helper cells that are the main source of the pro-inflammatory cytokine IL-17 and play a major role in periodontitis.

In periodontal disease, IL-17 contributes to tissue destruction by affecting which cell types?

Epithelial cells, fibroblasts (soft tissue), osteoblasts, and osteoclasts (bone).

In a healthy state, what is the role of IL-17 in the oral epithelium?

It helps maintain the mucosal barrier by upregulating tight junction proteins and inducing the secretion of antimicrobial peptides.