Hipersensitivitas Tipe 4 (Cell-mediated Hypersensitivity), Immunology

Summary

In this video, the presenter explains Type 4 hypersensitivity, also known as cell-mediated hypersensitivity, which is mediated by T-cells, either CD4+ (helper T-cells) or CD8+ (cytotoxic T-cells). The video covers how this hypersensitivity can be triggered by autoimmune reactions or environmental antigens, leading to localized, chronic, and progressive diseases like contact dermatitis or tuberculosis. The mechanisms involve T-cells activating macrophages and neutrophils or directly killing antigen-exposed cells. The video also discusses the treatment options, including anti-inflammatory steroids and monoclonal antibodies, to manage inflammation and control immune responses.

Takeaways

• 😀 Hypersensitivity Type 4, also known as cell-mediated hypersensitivity, is mediated by T cells, specifically CD4+ T helper cells and CD8+ cytotoxic T cells.
• 😀 CD4+ T helper cells release cytokines that activate macrophages and neutrophils, indirectly causing tissue damage.
• 😀 CD8+ cytotoxic T cells directly kill infected or damaged cells without needing assistance from other cells.
• 😀 Type 4 hypersensitivity can be triggered by autoimmune diseases or excessive immune responses to environmental antigens.
• 😀 Autoimmune diseases associated with Type 4 hypersensitivity are typically organ-specific and not systemic.
• 😀 Contact dermatitis is a common example of Type 4 hypersensitivity, where the immune system reacts to allergens such as Poison Ivy.
• 😀 The two mechanisms of damage in Type 4 hypersensitivity are indirect (via CD4+ T cells) and direct (via CD8+ T cells).
• 😀 Type 4 hypersensitivity reactions are delayed, often appearing 24-48 hours after exposure to the antigen due to the time it takes for T cells to respond.
• 😀 Chronic and progressive diseases are common in Type 4 hypersensitivity, meaning the condition can worsen over time with repeated antigen exposure or incomplete antigen removal.
• 😀 Treatments for Type 4 hypersensitivity include anti-inflammatory steroids (e.g., prednisone), TNF inhibitors (e.g., infliximab), and interleukin agonists (e.g., tocilizumab).
• 😀 Monoclonal antibody drugs used to treat Type 4 hypersensitivity often end in '-mab', signifying their production through monoclonal antibody techniques.

Q & A

What is Hypersensitivity Type 4, and how is it mediated?

Hypersensitivity Type 4 is also known as cell-mediated hypersensitivity, as it is mediated by T-cells. It can be mediated by CD4+ T-helper cells or CD8+ cytotoxic T-cells. These T-cells respond to antigens either from the environment or due to autoimmune reactions.

How does Hypersensitivity Type 4 differ from Hypersensitivity Type 3?

While Hypersensitivity Type 3 is immune complex-mediated, Type 4 is cell-mediated. Hypersensitivity Type 4 involves T-cells, which directly or indirectly cause tissue damage, whereas Type 3 involves the deposition of immune complexes that lead to inflammation and tissue injury.

What are some diseases associated with Type 4 hypersensitivity?

Diseases associated with Type 4 hypersensitivity include autoimmune conditions like dermatitis contact (skin allergies caused by substances like poison ivy) and tuberculosis (TB), which is caused by Mycobacterium tuberculosis. Both are mediated by T-cells.

How does the immune response in Type 4 hypersensitivity work?

In Type 4 hypersensitivity, T-helper cells (CD4+) release cytokines that activate macrophages and neutrophils, leading to tissue destruction. CD8+ cytotoxic T-cells directly kill infected or damaged cells through a more specific and direct mechanism.

What is the role of cytokines in Type 4 hypersensitivity?

Cytokines play a central role in Type 4 hypersensitivity by activating immune cells like macrophages and neutrophils. These cells then cause inflammation and tissue damage as part of the immune response against the perceived threat.

What is the difference between Type 4 hypersensitivity and Type 1 hypersensitivity?

Type 4 hypersensitivity is a delayed response, typically taking 24-48 hours to manifest, while Type 1 hypersensitivity is an immediate allergic reaction (like anaphylaxis) mediated by IgE antibodies and mast cells.

Why is Type 4 hypersensitivity considered chronic and progressive?

Type 4 hypersensitivity is considered chronic because the immune response often persists for long periods. It is progressive because repeated antigen exposure can exacerbate inflammation and tissue damage, leading to worsening symptoms over time.

What are the treatment options for Type 4 hypersensitivity?

Treatment for Type 4 hypersensitivity includes anti-inflammatory steroids like prednisone, dexamethasone, and triamcinolone, as well as tumor necrosis factor (TNF) inhibitors like adalimumab and golimumab. Interleukin agonists such as tocilizumab and dupilumab can also help reduce inflammation.

How does tuberculosis relate to Type 4 hypersensitivity?

Tuberculosis (TB) is caused by Mycobacterium tuberculosis, which stimulates a strong immune response mediated by T-cells. In TB, this immune response can lead to granuloma formation and tissue damage, which is characteristic of Type 4 hypersensitivity.

What does the term 'monoclonal antibody' (mAb) mean in relation to immunotherapy for Type 4 hypersensitivity?

A monoclonal antibody (mAb) refers to an antibody produced from a single clone of cells. These are used in immunotherapy to target specific immune system components, like TNF or interleukins, to reduce inflammation in conditions like Type 4 hypersensitivity.