Antibody structure The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region. (more) immunity biology Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/immunity-biology Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Harvard T.H. Chan School of Public Health - The Nutrition Source - Nutrition and Immunity Ask the Chatbot a Question Written by Written by Kara Rogers Kara Rogers is the senior editor of biomedical sciences at Encyclopædia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and... Kara Rogers Fact-checked by Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Oct. 20, 2025 •History Table of Contents Table of Contents Ask the Chatbot immunity, in biology, the ability of the body to prevent or defeat infection from invading microorganisms or parasites. This protection relies on the coordinated actions of the immune system. The body defends itself against infection through two main types of immunity: innate (or natural) and acquired. Innate immunity consists of defense mechanisms present at birth that act against a broad range of infectious agents, regardless of whether the body has encountered them before. The mechanisms...

　　Continue reading with Britannica Premium The trusted destination for facts and information 7-Day Free Trial, No Ads, Unlimited Access Subscribe Today