Immune System


The immune system attacks organisms and substances that invade body systems and cause disease.


Pathogen - a bacterium, virus, or other microorganism that can cause disease.

Active Immunity - the immunity that results from the production of antibodies by the immune system in response to the presence of an antigen.

Passive Immunity - the short-term immunity that results from the introduction of antibodies from another person or animal.

Antigen - a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

Antibody - a blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances that the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood.

Why Are Antibodies Ineffective Against Viruses?

Antibiotics are ineffective against viruses because viruses do not have cells. Viruses are infectious agents that live within the cells of other living things. Antibiotics work by breaking down the cell walls of bacteria or interfering with the bacteria's ability to repair its cell's DNA.


The human immunodeficiency virus (HIV) is a lentivirus that causes the acquired immunodeficiency syndrome, a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. AIDS is a chronic immune system disease caused by HIV (human immunodeficiency virus)


  • Fever.
  • Fatigue.
  • Swollen lymph nodes — often one of the first signs of HIV infection.
  • Diarrhea.
  • Weight loss.
  • Cough.
  • Shortness of breath.


  • More than 1.2 million people in the United States are living with HIV infection, and almost 1 in 7 (14%) are unaware of their infection.
  • Gay, bisexual, and other men who have sex with men (MSMa), particularly young black/African American MSM, are most seriously affected by HIV.
  • By race, blacks/African Americans face the most severe burden of HIV.


  • "The Cocktail"
  • Antiretrovirals (ARVs)
  • Highly Active Antiretroviral Therapy (HAART or ART)

Inflammatory Bowel Disease (IBD)

Inflammatory Bowel Disease is caused when the immune system attacks the lining of the intestines.


  • Episodes of diarrhea
  • Rectal bleeding
  • Urgent bowel movements
  • Abdominal pain
  • Fever
  • Weight loss


  • Approximately 1.6 million Americans currently have IBD, a growth of about 200,000 since the last time CCFA reported this figure (in 2011).

  • As many as 70,000 new cases of IBD are diagnosed in the United States each year.

  • There may be as many as 80,000 children in the United States with IBD.


Ulcerative colitis and Crohn's disease are the two major forms of IBD. Oral and injected immune-suppressing medicines can treat IBD.