The key difference between professional and non-professional antigen presenting cells is that professional antigen presenting cells are accessory cells expressing MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors, while non-professional antigen presenting cells are accessory cells expressing only MHC class I molecules.
An antigen-presenting cell is a cell that displays antigens bound by MHC proteins on its surface. It is also called an accessory cell. This process is known as antigen presentation. Therefore, the basic function of an antigen-presenting cell is processing antigens and presenting them to T cells. Moreover, T cells can recognize these complexes by using their T cell receptors (TCRs). Professional and non-professional antigen-presenting cells are two different types of antigen-presenting cells.
CONTENTS
1. Overview and Key Difference
2. What are Professional Antigen Presenting Cells
3. What are Non-professional Antigen Presenting Cells
4. Similarities – Professional and Non-professional Antigen Presenting Cells
5. Professional vs Non-professional Antigen Presenting Cells in Tabular Form
6. Summary – Professional vs Non-professional Antigen Presenting Cells
What are Professional Antigen Presenting Cells?
Antigen-presenting cells that express MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors are often called professional antigen-presenting cells. The term “antigen-presenting cell” is used specifically to describe professional antigen-presenting cells. However, non-professional antigen-presenting cells are also capable of antigen-presenting through MHC class I molecules.
Figure 01: Professional Antigen Presenting Cells
Professional antigen-presenting cells are very efficient at internalizing antigens through phagocytosis or receptor-mediated endocytosis. Then these cells process the antigens into peptide fragments and display those peptides which are bound to MHC class II molecules on their membrane. Later, T cells recognize and interact with the antigen-MHC class II complex on the membrane of the professional antigen-presenting cell. An additional co-stimulatory signal is also produced by these professional antigen-presenting cells, leading to activation of T cells. All professional antigen-presenting cells can express MHC class I molecules. There are three main types of professional antigen-presenting cells: dendritic cells, macrophages and B cells. Furthermore, dendritic cells present foreign antigens to both helper and cytotoxic T cells, while macrophages and B cells present foreign antigens only to helper T cells.
What are Non-professional Antigen Presenting Cells?
Antigen-presenting cells that express only MHC class I molecules are often called non-professional antigen-presenting cells. Non-professional antigen-presenting cells include all nucleated cell types in the human body. These cells use an MHC class I molecule coupled to beta-2 microglobulin to display endogenous peptides on the cell membrane. The peptides originate inside the cells; therefore, they are known as endogenous peptides (endogenous antigens).
Figure 02: Non-professional Antigen Presenting Cells
Cytotoxic T cells are able to interact with endogenous antigens presented using an MHC class I molecule. Virus-infected cells and cancer cells are non-professional antigen-presenting cells that can present antigens originating inside them to cytotoxic T cells. Non-professional antigen-presenting cells do not typically express MHC class II molecules.
Similarities Between Professional and Non-professional Antigen Presenting Cells
- Professional and non-professional antigen-presenting cells are two different types of antigen-presenting cells.
- Both types can present antigens to T cells via MHC proteins on their cell membrane surface.
- Both types can process antigens before presenting them to T cells.
- They are also known as accessory cells.
- They play a vital role in the adaptive immune system of the body.
Difference Between Professional and Non-professional Antigen Presenting Cells
Professional antigen-presenting cells are accessory cells that express MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors, while non-professional antigen-presenting cells are accessory cells that express only MHC class I molecules. Thus, this is the key difference between professional and non-professional antigen-presenting cells. Furthermore, professional antigen-presenting cells can present antigens to both helper and cytotoxic T cells. On the other hand, non-professional antigen-presenting cells can present antigens only to helper T cells.
The below infographic presents the differences between professional and non-professional antigen-presenting cells in tabular form for side by side comparison.
Summary – Professional vs Non-professional Antigen Presenting Cells
Antigen-presenting cells regulate the process of antigen presentation to T cells via MHC proteins on their cell membrane surface. There are two types of antigen-presenting cells as professional and non-professional antigen-presenting cells. These play a vital role in the adaptive immune system of the body. Professional antigen-presenting cells are accessory cells that express MHC class II molecules along with co-stimulatory molecules and pattern recognition receptors, while non-professional antigen-presenting cells are accessory cells that express only MHC class I molecules. So, this summarizes the difference between professional and non-professional antigen presenting cells.