Editing Immune response (section)

== Adaptive part ==
{{Further|Adaptive immune response}}
[[File:Activation_of_T_and_B_cells.png|thumb|[[MHC class II|MHC]] [[peptide]] presentation along with co-stimulatory [[ligand]]/[[immune receptor|receptor]] binding]]

The [[adaptive immune response]] is the body's [[defence in depth|second line of defense]]. The cells of the adaptive immune system are extremely specific because during early developmental stages the B and T cells develop antigen receptors that are specific to only certain [[antigen]]s. This is extremely important for B and T cell activation. B and T cells are extremely dangerous cells, and if they are able to attack without undergoing a rigorous process of activation, a faulty B or T cell can begin exterminating the host's own healthy cells.<ref name="Bonilla_2010">{{cite journal|vauthors=Bonilla FA, Oettgen HC|date=February 2010|title=Adaptive immunity|journal=The Journal of Allergy and Clinical Immunology|volume=125|issue=2 Suppl 2|pages=S33–S40|doi=10.1016/j.jaci.2009.09.017|pmid=20061006}}</ref> Activation of naïve helper T cells occurs when [[Antigen-presenting cell|antigen-presenting cells (APCs)]] present foreign antigen via [[MHC class II|MHC class II molecules]] on their cell surface. These APCs include [[dendritic cells]], [[B cell]]s, and [[macrophages]] which are specially equipped not only with MHC class II but also with co-stimulatory ligands which are recognized by co-stimulatory receptors on helper T cells. Without the co-stimulatory molecules, the adaptive immune response would be inefficient and T cells would become [[anergic]]. Several T cell subgroups can be activated by specific APCs, and each T cell is specially equipped to deal with each unique microbial pathogen. The type of T cell activated and the type of response generated depends, in part, on the context in which the APC first encountered the antigen.<ref name="Janeway">{{cite book|url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=imm.TOC&depth=10|title=Immunobiology|vauthors=Janeway CA, Travers P, Walport M, Shlomchik MJ|publisher=Garland Science|year=2001|isbn=0815341016|edition=5th|location=New York and London}}</ref> Once helper T cells are activated, they are able to activate naïve B cells in the [[lymph node]]. However, B cell activation is a two-step process. Firstly, B cell receptors, which are just [[Immunoglobulin M]] (IgM) and [[Immunoglobulin D]] (IgD) antibodies specific to the particular B cell, must bind to the antigen which then results in internal processing so that it is presented on the MHC class II molecules of the B cell. Once this happens a T helper cell which is able to identify the antigen bound to the MHC interacts with its co-stimulatory molecule and activates the B cell. As a result, the B cell becomes a [[plasma cell]] which secretes antibodies that act as an [[opsonin]] against invaders.{{citation needed|date=July 2022}}

Specificity in the adaptive branch is due to the fact that every B and T cell is different. Thus there is a diverse community of cells ready to recognize and attack a full range of invaders.<ref name="Bonilla_2010" /> The trade-off, however, is that the adaptive immune response is much slower than the body's innate response because its cells are extremely specific and activation is required before it is able to actually act. In addition to specificity, the adaptive immune response is also known for [[immunological memory]]. After encountering an antigen, the immune system produces memory T and B cells which allow for a speedier, more robust immune response in the case that the organism ever encounters the same antigen again.<ref name="Bonilla_2010" />