Editing Humoral immunity (section)

== Antibody production ==
In humoral immune response, the naive [[B cell|B cells]] begin the maturation process in the bone marrow, gaining [[B-cell receptor|B-cell receptors (BCRs)]] along the cell surface.<ref>{{Cite journal |last=Boundless |date=2016-05-26 |title=Humoral Immune Response |url=https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-immune-system-42/adaptive-immune-response-234/humoral-immune-response-875-12125/ |url-status=dead |journal=Boundless |language=en |archive-url=https://web.archive.org/web/20161012223311/https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-immune-system-42/adaptive-immune-response-234/humoral-immune-response-875-12125/ |archive-date=2016-10-12 |access-date=2017-04-15}}</ref> These BCRs are membrane-bound protein complexes that have a high binding affinity for specific [[Antigen|antigens]]; this specificity is derived from the amino acid sequence of the heavy and light polypeptide chains that constitute the [[variable region]] of the BCR. <ref>{{Cite journal |last=Eisen |first=Herman N. |date=2014-05-01 |title=Affinity Enhancement of Antibodies: How Low-Affinity Antibodies Produced Early in Immune Responses Are Followed by High-Affinity Antibodies Later and in Memory B-Cell Responses |url=https://aacrjournals.org/cancerimmunolres/article/2/5/381/467427/Affinity-Enhancement-of-Antibodies-How-Low |journal=Cancer Immunology Research |language=en |volume=2 |issue=5 |pages=381–392 |doi=10.1158/2326-6066.CIR-14-0029 |pmid=24795350 |issn=2326-6066|url-access=subscription }}</ref> Once a BCR interacts with an antigen, it creates a binding signal which directs the B cell to produce a unique [[antibody]] that only binds with that [[antigen]]. The mature B cells then migrate from the bone marrow to the lymph nodes or other [[Lymphatic system|lymphatic organs]], where they begin to encounter pathogens.

[[File:Humoral Response Drawing.svg|thumb|Step 1: A macrophage engulfs the pathogen. Step 2: The macrophage then digests the bacterium and presents the pathogen's antigens. Step 3: A T helper cell binds to the macrophage and becomes an activated T helper cell. Step 4: The activated T helper cell binds to a B cell in order to activate the B cell. Step 5: When the B cells are activated, some B cells turn into plasma cells and are released in the blood, while other B cells become B memory cells that quicken response for a second exposure. Step 6: Plasma cells then secrete antibodies, which bind to antigens to fight the invading pathogens.]]

=== B cell activation ===
When a B cell encounters an antigen, a signal is activated, the antigen binds to the receptor and is taken inside the B cell by [[endocytosis]]. The antigen is processed and presented on the B cell's surface again by [[MHC class II|MHC-II proteins]]. The MHC-II proteins are recognized by [[T helper cell|helper T cells]], stimulating the production of proteins, allowing for B cells to multiply and the descendants to differentiate into antibody-secreting cells circulating in the blood.<ref name="auto">{{Cite journal| vauthors = Janeway Jr CA, Travers P, Walport M, Shlomchik MJ |date=2001|title=B-cell activation by armed helper T cells |url=https://www.ncbi.nlm.nih.gov/books/NBK27142/|journal=Immunobiology: The Immune System in Health and Disease. | edition = 5th |language=en}}</ref> B cells can be activated through certain microbial agents without the help of [[T cell|T-cells]] and have the ability to work directly with antigens to provide responses to pathogens present.<ref name="auto"/>

=== B cell proliferation ===
The B cell waits for a helper T cell (T<sub>H</sub>) to bind to the complex. This binding will activate the T<sub>H</sub> cell, which then releases [[cytokine]]s that induce B cells to divide rapidly, making thousands of identical clones of the B cell. These daughter cells either become [[plasma cell]]s or [[Memory B cell|memory cells]]. The memory B cells remain inactive here; later, when these memory B cells encounter the same antigen due to reinfection, they divide and form plasma cells. On the other hand, the plasma cells produce a large number of antibodies which are released freely into the [[circulatory system]].

=== Antibody-antigen reaction ===
These antibodies will encounter antigens and bind with them. This will either interfere with the chemical interaction between host and foreign cells, or they may form bridges between their antigenic sites hindering their proper functioning. Their presence might also attract macrophages or killer cells to attack and [[Phagocytosis|phagocytose]] them.