Th1 vs Th2 reponse

Th1 (T-helper 1) and Th2 (T-helper 2)

subsets of CD4+ T-helper cells that drive different types of immune responses.

Their activation and cytokine production patterns are crucial in determining the nature of immune responses to infections, autoimmune diseases, and allergic conditions.

Development and Differentiation

• Th1 Response: Differentiation is driven by IL-12 and IFN-γ.

• Th2 Response: Differentiation is driven by IL-4.

Key Transcription Factors:

• Th1: T-bet (drives Th1 differentiation)

• Th2: GATA3 (drives Th2 differentiation)

Th1 Cytokines:

• IFN-γ (Interferon-gamma): Activates macrophages, promotes cytotoxic T cell responses.

• IL-2: Promotes T cell proliferation.

• TNF-α: Promotes inflammation and activates immune cells.

Th2 Cytokines

• IL-4: Promotes B cell differentiation, antibody production, especially IgE.

• IL-5: Activates eosinophils (important in allergic responses).

• IL-13: Stimulates mucus production and airway remodeling, involved in allergic responses.

Th1 Response

Primarily involved in cell-mediated immunity, targeting intracellular pathogens (e.g., viruses, certain bacteria) and tumors.

• Activates macrophages to destroy infected cells.

• Promotes CD8+ T cell (cytotoxic T cell) activation.

• Important in delayed-type hypersensitivity (DTH).

Th2 Response

Primarily involved in humoral immunity, defending against extracellular parasites (e.g., helminths) and involved in allergic reactions.

• Activates B cells to produce antibodies (IgE, IgG).

• Promotes eosinophil, basophil, and mast cell activation, contributing to allergy and asthma.

Role in Disease Th1

• Associated with autoimmune diseases like Multiple Sclerosis, Type 1 Diabetes, and Crohn's Disease.

• Can contribute to chronic inflammation.

Role in Disease Th2

• Associated with allergic diseases like asthma, rhinoconjunctivitis, and eczema.

• Drives IgE production and eosinophilia (common in parasitic infections and allergic conditions).

Th1/Th2 Balance

Th1 and Th2 responses can inhibit each other:

• IFN-γ (Th1 cytokine) inhibits IL-4 (Th2 cytokine) production, and vice versa.

• The balance between these two responses determines the outcome of many immune-related conditions.

Th17

Another subset of T-helper cells (distinct from Th1 and Th2) that plays a role in autoimmunity and inflammation, especially in diseases like psoriasis and rheumatoid arthritis.

Th1 Dominant Conditions

• Chronic infections (e.g., tuberculosis, leprosy)

• Autoimmune diseases (e.g., rheumatoid arthritis, Crohn's)

Th2 Dominant Conditions

• Allergic diseases (e.g., asthma, eczema, hay fever)

• Parasitic infections (e.g., helminths)

Th1 modulation:

• Immunosuppressive therapies (e.g., corticosteroids) for autoimmune diseases.

• IFN-γ therapy for certain infections.

Th2 modulation

• Anti-IgE therapies (e.g., omalizumab) for allergies.

• Corticosteroids and antileukotriene drugs in asthma management.