Innate immunity is the first line of defence against invading pathogens, but it is not always
sufficient to provide full protection. This is where the adaptive immune system comes in.
The adaptive immune system is highly specific and can recognize and respond to a wide
range of pathogens. However, it takes time to develop a response, and it requires prior
exposure to the pathogen or a vaccine.
The interface between innate and adaptive immunity is crucial for mounting an effective
immune response. Dendritic cells (DCs) are the key players in this process, as they can
bridge innate and adaptive immunity by presenting antigens to T and B cells. DCs are unique
among immune cells in their ability to take up, process, and present antigens to T cells, and
to provide co-stimulatory signals that activate T cell responses.
Complement (C) is another important link between innate and adaptive immunity.
Complement is a series of plasma proteins that can be activated by different stimuli, such as
pathogens, immune complexes, or damaged cells. Complement activation results in the
recruitment and activation of various immune cells, such as phagocytes, and the formation
of membrane attack complexes that can kill pathogens. Complement can also interact with
DCs and enhance their antigen-presenting capacity.
Innate immunity plays an instructive role in shaping the adaptive immune response. Innate
immune cells can produce cytokines and chemokines that can influence the differentiation
and activation of T and B cells. For example, innate immune cells can produce interleukin-12
(IL-12), which can promote the differentiation of T helper 1 (Th1) cells that produce
interferon-gamma (IFN-γ) and activate macrophages to kill intracellular pathogens. Innate
immune cells can also produce interleukin-4 (IL-4), which can promote the differentiation of
T helper 2 (Th2) cells that produce interleukin-5 (IL-5) and activate eosinophils to kill
extracellular parasites.
Innate immunity can also trigger inflammation, which is a hallmark of the immune response
to infection and tissue damage. Inflammation is mediated by various immune cells and
molecules, such as neutrophils, macrophages, cytokines, and chemokines. Inflammation can
be beneficial by promoting the recruitment of immune cells and the elimination of
pathogens. However, excessive or chronic inflammation can be detrimental and contribute
to tissue damage, autoimmune diseases, and cancer.
Questions:
What is the role of dendritic cells in bridging innate and adaptive immunity?
What is complement, and how does it link innate and adaptive immunity?
How does innate immunity play an instructive role in shaping the adaptive immune
response?
What is the role of inflammation in the immune response?
How can chronic inflammation contribute to disease?