In human blood, there are three main types of dendritic cells (DCs) that play a crucial role in the immune system. These specialized immune cells act as messengers between the innate and adaptive immune responses, capturing antigens and presenting them to T cells.
Based on surface marker expression and function, the different types of DCs found circulating in the blood are clearly defined. Understanding these types is key to appreciating their specific roles in initiating immune responses against pathogens and even in tolerance.
Types of DC Cells in Human Blood
According to current definitions, three types of DCs have been identified in human blood. These are distinguished by specific cell surface markers:
- CD1c+ Myeloid DCs: These are a major subset of conventional or classical DCs (cDCs).
- CD141+ Myeloid DCs: Also known as cDC1s, these represent another distinct subset of conventional DCs.
- CD303+ Plasmacytoid DCs: These cells are different from myeloid DCs and are primarily known for their role in producing large amounts of type I interferons, especially in response to viral infections.
These types represent the circulating precursors or subsets that migrate into tissues to perform their antigen-presenting functions.
Detailed Overview of DC Subtypes
Let's look closer at each type:
| Type of DC Cell | Key Surface Marker | Description | Primary Role (General) |
|---|---|---|---|
| CD1c+ Myeloid DCs | CD1c (BDCA-1) | Conventional DCs (cDC2s); abundant in blood and many tissues. | Present antigens, activate T cells (especially CD4+). |
| CD141+ Myeloid DCs | CD141 (BDCA-3) | Conventional DCs (cDC1s); less abundant than CD1c+ DCs. | Cross-present antigens to activate CD8+ T cells. |
| CD303+ Plasmacytoid DCs | CD303 (BDCA-2) | Plasmacytoid appearance; often considered innate immune cells due to function. | Produce type I interferons; involved in antiviral immunity. |
CD1c+ Myeloid DCs (also known as cDC2s) are particularly efficient at activating helper T cells (CD4+ T cells) and are important for immunity against extracellular pathogens. They express markers like CD1c and are found in various tissues throughout the body.
CD141+ Myeloid DCs (cDC1s) are specialized in capturing antigens from dead cells and presenting them via MHC class I molecules. This process, called cross-presentation, is crucial for activating cytotoxic T lymphocytes (CD8+ T cells), which are vital for clearing viral infections and tumor cells. They are characterized by the expression of CD141.
CD303+ Plasmacytoid DCs (pDCs) have a different origin and morphology compared to myeloid DCs. They resemble plasma cells and are primarily found in the blood and lymphoid organs. Their main function is recognizing viral nucleic acids through Toll-like receptors (TLRs) and producing massive amounts of type I interferons (IFN-alpha, IFN-beta), making them key players in the immediate response to viral infections. They express markers like CD303.
These distinctions highlight the specialized functions of different DC subsets, allowing the immune system to mount tailored responses to various threats.
