The immune system is the body's natural defense system against invading pathogens. It protects the body from infection and works to communicate an individual's well-being through a complex network of interconnected cells and cytokines. This system is an associated host defense. An uncontrolled immune system has the potential to trigger negative complications in the host. Type 1 diabetes results from the destruction of pancreatic beta-cells by a beta-cell-specific autoimmune process. Examples of beta-cell autoantigens are insulin, glutamic acid decarboxylase, tyrosine phosphatase, and insulinoma antigen. There are many autoimmune diseases, but type 1 diabetes mellitus is one of the well-characterized autoimmune diseases. The mechanisms involved in the beta-cell destruction are still not clear; it is generally believed that beta-cell autoantigens, macrophages, dendritic cells, B lymphocytes, and T lymphocytes are involved in the beta-cell-specific autoimmune process. It is necessary to determine what exact factors are causing the immune system to become unregulated in such a manner as to promote an autoimmune response. (C) 2014 Elsevier B.V. All rights reserved.