Difference Between TH1 and TH2 Helper Cells

Key Difference – TH1 vs TH2 Helper Cells
 

Type 1 T helper (TH1) cells and Type 2 T helper (TH2) cells are two sub types of T helper cells that can be distinguished by the type of cytokines that they secrete. TH1 cells secrete interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α) and mainly protect the organism against intracellular pathogens. TH2 cells secrete interleukins 4, 5, 10, and 13 (IL-4, IL-5, IL-10, and IL-13) and mainly protect the organism against extracellular pathogens. This is the key difference between TH1 and TH2.

White blood cells are an integral part of our immune system. These cells protect our bodies from infectious diseases and foreign antigens. There are several types of white blood cells. Among them, lymphocyte is a subtype. Three types of lymphocytes are found in vertebrate immune system namely, T cells, B cells and Natural killer cells. T cells or thymus cells are one of the major cellular components in the adaptive immune response. They recognize foreign antigens and involve in cell mediated immunity. T cells are characterized by the presence of T cell receptors on the cell surfaces. T cells or T lymphocytes are several major types among them T helper cells also known as CD4⁺ T cells are one type. T helper cells express CD4 glycoprotein on their cell surfaces, and they become activated when peptide antigens are presented by MHC class II molecules. Upon activation, T helper cells multiply rapidly and secrete cytokines and growth factors that assist and regulate other immune cells and responses. Helper T cells can be differentiated into different subtypes such as TH1, TH2, TH3, TFH, TH17 and TH9. These subtypes secrete different cytokines that facilitate different types of immune responses.

CONTENTS

1. Overview and Key Difference
2. What are TH1 Helper Cells
3. What are TH2 Helper Cells
4. Similarities Between TH1 and TH2 Helper Cells
5. Side by Side Comparison – TH1 vs TH2 Helper Cells in Tabular Form
6. Summary

What are TH1 Cells?

Type 1 T helper (TH1) cells are a type of helper T cells that are differentiated from naïve T helper cells. TH1 cells differ from other T helper cells functionally due to the secretion of different cytokines. TH 1 cells secrete interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α). By this cytokine secretion, it can be distinguished from Type 2 helper cells easily.

TH1 cells are also activating the macrophages to destroy microbes trapped within the macrophages’ phagosomes. They are also contributing to the activation of cytotoxic T cells to destroy infected cells. By looking at the functions of TH1 cells, it is clear that TH1 cells are mainly involving with the defending of the organism from intracellular pathogens. And also TH1 cells stimulate B cells to secrete specific antibodies such as IgG, which is necessary to coat extracellular microbes.

What are TH2 Cells?

Type 2 helper T cells (TH2 cells) are another type of T helper cells that are differentiated from naïve T helper cells. TH2 cells secrete interleukins 4, 5, 10, and 13 (IL-4, IL-5, IL-10, and IL-13) and mainly involve in defending the organism against extracellular pathogens.

TH2 cells are able to activate B cells to produce most of the antibodies against antigens including IgE and some classes of IgG that bind to mast cells, basophils and eosinophils. And also TH2 cells are involved with releasing local mediators that cause sneezing, coughing, or diarrhoea to expel extracellular microorganisms.

What are the Similarities Between TH1 and TH2 Helper Cells?

• Both TH1 and TH2 cells are produced when naïve T helper cells become active in the peripheral lymphoid tissue.
• Both cells produce cytokines that are necessary to activate other immune cells.
• Both provide the basis for the development of new vaccines.
• Both cells provide the basis for the development of new therapeutic pathways for allergic and autoimmune disorders.
• Both cells initially express CCR7 (CC chemokine receptor 7).

What is the Difference Between TH1 and TH2 Helper Cells?

Summary –TH1 vs TH2 Helper Cells

T helper cells are one of the important cells in the adaptive immunity. They activate B cells, macrophages and cytotoxic T cells to produce antibodies against foreign antigens, to destroy ingested microbes and to destruct infected target cells respectively.  Type 1 helper T cells and type 2 helper T cells are two subtypes of helper T cells. These two types are functionally different and can be differentiated by the type of cytokines they secrete. Th1 cells secrete interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α) while Th2 cells secrete interleukins 4, 5, 10, and 13 (IL-4, IL-5, IL-10, and IL-13). Th1 cells carry out cell mediated immunity while TH2 cells provide humoral immunity. This is the difference between TH1 and TH2 cells.

Reference:

1.Alberts, Bruce. “Helper T Cells and Lymphocyte Activation.” Molecular Biology of the Cell. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1970. Available here  
2.“T-Cell Subsets (Th1 versus Th2).” Annals of Allergy, Asthma & Immunology, Elsevier, 23 Feb. 2010. Available here   

Image Courtesy:

1.’Th1-Th2-Th17-Treg origin’ (CC BY-SA 3.0) via Commons Wikimedia 
2.’Lymphocyte activation simple’By Häggström, Mikael (2014). “Medical gallery of Mikael Häggström 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. (Public Domain) via Commons Wikimedia