An 'antigen' is

An antigen is

Given below are two statements :

Statement $I$ : Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.

Statement $II$ : Both bone marrow and thymus provide micro environments for the development and maturation of T-lymphocytes.

In the light of above statements, choose the most appropriate answer from the options given below :

Define : Autoimmunity

Assertion : Interferons are effective against viruses.

Reason : Proteins which can be synthesized only by genetic engineering are effective against viruses.