Question

Be able to identify and explain ways where innate and adaptive immunity are interconnected.

Answer 1

Innate immunity is what is first line of defence whenever a microbe or damaged tissue is encountered. Innate immunity leads to activation of adaptive immunity which is how they are interconnected.

Before seeing how is interconnected we should have little insight in their mechanism of action

Innate Immunity :

Epithelial cells : By acting as barrier and releasing defensins

Dendritic cells : Recognize the antigen and present it to T cells

Nature killer cells

Macrophages, Neutrophils

Whereas Adaptive immunity is composed of :

Humoral immunity mediates by B lymphocytes which form antibodies

Cell mediated immunity by T lymphocytes which activate other cells by activation of CD4+ T cells. o kill the cell directly by CD8 + T cells

How is innate immunity and adaptive immunity interconnected but ?

The phagocytes like macrophage and dendritic cells are called as Antigen presenting cells (APC's) . They ingest the antigen and complex it with Major histocompatibilty complex (MHC) and this complex is translocated on their membranes, expressing the antigens which they present to T cells leading to their activation and hence the adaptive response

MHC-1 cause activation of CD8+T cells expressed on platelets , tumor cells expressing intracellular antigens , tumor proteins. CD8 tells kills the cell directly on activation.

MHCII activates CD4+ T cells and is present on all nucleated cells expressing the antiges of extracellular microbes.CD4+ T cells on activation release arsenal of cytokines which activate cells like macrophages and kill the cell.

Another mechanism of connectivity is :

Pathogens and Damaged tissue have Associated patterns like pathogen assoicated patterns and damaged tissue associated patterns respectively. These are recognised by pattern associated receptors (PRP's). These are expressed on cells of innate immunity. They are :

1- Toll like receptors (TLR)

2- Nod like receptors (NLR)

3-Mannose binding lectins

4-G protein coupled receptors

These recognize the associated proteins and activate signalling pathways which lead to release of inflammosome activation leading to production of cytokines like IL-1 etc . These all activate the cells of adaptive immunity. This is how they are interconnected by :

1- APC's

2-PRP's