 The complicated role CD80 plays in immune system regulation presents an opportunity for CD80 interactions to go rogue in various diseases.The up-regulation of CD80 has been linked to various autoimmune diseases, including 
multiple sclerosis, systemic lupus erythematosus and sepsis (which may partly be due to over-active T-cells), and CD80 has also been shown to help spread of HIV infection in the body.CD80 is also linked to various cancers, though some experience CD80 induced tolerance via possible regulatory T cell interaction and others experience inhibited growth and metastasis related to CD80 up-regulation, further exemplifying the complicated role CD80 plays.