What is the Difference Between Naive and Effector T Cells

The main difference between naïve T cells and effector T cells is that naïve T cells occur in the lymphoid tissue, while effector T cells arise in non-lymphoid tissue. 

Naïve and effector T cells are T lymphocytes, white blood cells in the immune system. Both play a crucial role in the adaptive immune system. 

Key Areas Covered

1. What are Naive T Cells
– Definition, Structure, Function
2. What are Effector T Cells
– Definition, Structure, Function
3. Similarities Between Calcium Naive and Effector T Cells
– Outline of Common Features
4. Difference Between Naive and Effector T Cells
– Comparison of Key Differences

Key Terms 

Effector T Cells, Naïve T Cells

What are Naïve T Cells

Naïve T cells are the T cells that occur in the thymus. Thymus is a primary lymphoid organ responsible for the production and maturation of lymphocytes. Therefore, naïve T cells are not activated cells. The main characteristics of naïve T cells include the presence of L-selectin (CD62L) and C-C Chemokine receptor type 7 (CCR7) and the absence of the activation markers, including CD25, CD44, or CD69 and memory CD45RO isoform. On the other hand, T cells play a critical role in the adaptive immune system. They respond to novel pathogens and initiate immune responses. This results in the activation of naïve T cells. Also, this allows the upregulation of surface markers of the naïve T cells.

Figure 1: T Cell and B Cell Activation

Furthermore, recognized antigen binds to the T cell receptor (TCR) located on the cell membrane of naïve T cells. 

What are Effector T Cells

Effector T cells are activated T cells. There are three types of effector cells. They are cytotoxic (killer) T cells, TH1 cells, and TH2 cells. Both helper and cytotoxic T cells recognize various antigens in the circulation system, which are shredded by pathogens. These antigens should be presented on the surfaces of the antigen-presenting cell (APS). Macrophages, dendritic cells, Langerhans cells, and B cells are the types of APSs. These APSs phagocytize pathogens and present the epitopes on their surfaces. The molecules that present those epitopes on the surface of the APSs are called major histocompatibility complexes (MHC).

Figure 2: CD8+ T Cell-Mediated Destruction of Infected Cells

Moreover, the two types of MHC complexes are MHC class I and MHC class II. The MHC class I molecules occur on the surface of the cytotoxic T cells, while MHC class II molecules appear on the surface of the helper T cells. Besides, T cells’ T cell receptors (TCR) bind with the MHC molecules on the APSs. Furthermore, two types of coreceptors stabilize this binding. They are CD4 coreceptors and CD8 coreceptors. The CD4 coreceptors arise on the surfaces of the helper T cells, and the CD8 coreceptors occur on the surface of the cytotoxic T cells. At the same time, the CD3 molecules on the surface of the cytotoxic T cells transmit the signals to the cell about the binding of the MHC complex to the T cell.

Similarities Between Naive and Effector T Cells

• Naïve and effector T cells are T lymphocytes that belong to the immune system.
• They play a vital role in adaptive immunity.
• They involve in cell-mediated immunity. 

Difference Between Naive and Effector T Cells

Definition

Naive T cells are stem cells that mature in the thymus and move into the lymphatic system. At the same time, effector T cells refer to a group of cells that includes several T cell types that actively respond to a stimulus, such as co-stimulation. 

Occurrence

Naïve T cells occur in the lymphoid tissue, while effector T cells in non-lymphoid tissue. 

Active Cells

Naïve T cells are not activated cells, while effector T cells are activated cells.  

Function

Naïve T cells undergo activation by antigen-presenting cells, while effector T cells secrete cytokines that activate innate leukocytes, support B and Tc cell activation, and induce regulatory lymphocytes. 

Conclusion

In brief, Naïve T cells and effector T cells are T lymphocytes in the immune system. Naïve T cells occur in the thymus, and they are not activated cells. Their function is to activate antigen-presenting cells. In comparison, effector T cells are the activated T cells in non-lymphoid tissue. Also, effector T cells secrete cytokines, activating inactive lymphocytes such as B and TC cells. Therefore, the main difference between naïve T cells and effector T cells is their activation and function. 

References:

1. Naive T cell. Naive T Cell – an overview | ScienceDirect Topics. (n.d.). 
2. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; 2001. General properties of armed effector T cells.

Image Courtesy:

1. “Activation of T and B cells” By Immcarle105 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “CD8+ T cell destruction of infected cells.” By Dananguyen – Own Work (CC-BY SA 4.0) via Commons Wikimedia