Red blood cells An image of human red blood cells (magnification x4000). (more) Why Are There Different Blood Types? Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/Why-Are-There-Different-Blood-Types 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 Ask the Chatbot a Question Written and fact-checked by The Editors of Encyclopaedia Britannica 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. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Mar 4, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot Different blood groups are the result of genetic variations that determine the presence or absence of specific antigens on the surface of red blood cells. These variations arise due to differences in genes that are inherited from parents, and they have evolved over time to serve various biological and immunological functions, such as influencing immune responses to infection and, in some instances, providing resistance to disease. The ABO blood group system, discovered by Karl Landsteiner in 1901, is one of the most well-known systems. It classifies blood into four types—A, B, AB, and O—based on the presence or absence of ...(100 of 319 words)

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