The immune response is the body's defense mechanism against the pathogens. The immune response of the body protects it from bacteria, viruses and multiple other disease causing organisms. The normal development of this protective immune response of the body is produced by as a result of the hormones which are produced by the thymus gland. The thymus gland produces the T-lymphocytes, which are important for a healthy immune response. The thymus gland secretes thymosin which is crucial for the development of these cells.
Hence, the answer is 'thymus gland'.
