Clinical immunology is the study of diseases caused by disorders of the immune system (i.e., failure, aberrant action, or malignant growth of the cellular elements of the system). It also involves diseases of other systems, where immune reactions play a part in the pathology or clinical features.

1. Immune deficiency diseases in which parts of the immune system fail to provide an adequate response to infectious disease agents and where the patient suffers from increased frequency of infectious diseases
2. Allergy and different hypersensitivities, in which the immune system responds inappropriately or too intensely to harmless substances in the environment (e.g., hayfever, asthma and other allergies)
3. Autoimmune diseases in which in which the immune system attacks its own host's body cells (examples include systemic lupus erythematosus, rheumatoid arthritis, autoimmune thyroiditis (Hashimoto's disease) and myasthenia gravis).
4. Certain forms of cancer in which certain cells of the immune system become malignant, e.g., leukemia or lymphoma, or where a depressed immune system can lead to malignancies in other non-immune body systems, e.g., breast cancer, GI cancer.