INNATE AND ADAPTIVE IMMUNITY CELL TYPES

The immune system has two important branches, Innate and adaptive immunity. It plays an essential role for health and the start and progression of chronic inflammation.

 Innate immune response

Innate immunity constitutes the host's first line of defense against danger signals in a rapid and non-specific manner.

During the first hours and days of an infection, invasion by pathogens induces the activation of innate immune cells. Among theme macrophages, monocytes, or NK-cells or humoral factors such as complement.

Macrophages and dendritic cells, together called antigen-presenting cells (APCs). They constitute the body’s main danger sensors and pioneer of an immune response. They constantly sample their environment, phagocytes all debris, present findings on their surface via major histocompatibility complex (MHC) molecules. After that, they send signals or interact with other immune cells when they encounter danger.

 Adaptive immune response

In contrast to the innate immune system, the adaptive immune response is antigen-specific. It includes cell-mediated (T cell) and humoral-mediated (B cell) immunities. They are both critical to drive tissue inflammation or repair. Antibody production, marking B cell response, play an important role in both innate and adaptive immunity.

T and B cells (lymphocytes) rearrange their genomes and create unique antigen-specific receptors. These are T cell receptors (TCRs) and B cell receptors (BCRs). There are two main types of T cells: CD8 and CD4.

• CD8 T lymphocytes are crucial for the limitation of viral spread through their cytotoxic function. They function via their TCR in recognizing foreign antigens (viruses...) on MHCI.
• CD4 T cells are essential for the expansion of CD8 T cells and the generation of CD8 memory T cells. CD4 are also necessary for the production of memory B cells (MBCs) and plasma cells. In contrast, CD4 T cells recognize antigen-loaded onto MHC class II. This via cells expressing and presenting antigens like macrophages, monocytes, dendritic cells, and B cells.
This type of immune response generates long-lasting immune memory ^(1,2,6).

The recognized characteristic of the innate and adaptive immune system is ''immune memory''. It enhances host survival upon reinfection.
Studies demonstrate that induction of innate immune memory in vivo takes place in two main compartments.

• At the center of the bone marrow, influencing the functional program of immune cell progenitors.
• At the periphery in the tissues ⁽²⁾.

You can check the biomarker list included in this pathway, see below: