Damage to thymus in a child may lead to:

Thymus is the primary lymphocyte, which is involved the production and maturation of T lymphocytes. T lymphocytes provide cell mediated immunity. B cells, which mature in the bone marrow, are responsible for antibody-mediated immunity. Related Theory Immature T lymphocytes are cells that have not yet encountered their specific antigen. In peripheral lymphoid organs, they can interact with antigen-presenting cells (APCs), which use MHC molecules to present antigen. Once the $T$ lymphocytes recognise their specific antigens, they proliferate and differentiate into one of several effector $T$ lymphocyte subsets. Effector T lymphocytes interact with host cells (rather than the pathogen) to carry out their immune function. T lymphocytes use co-receptors to bind to the MHC molecules. Co-receptors can be either CD4 or $C D_8$. CD proteins help to differentiate major groups of effector $T$ lymphocytes. immature $C_{8+} T$ lymphocytes will become cytotoxic $T$ lymphocytes. Alternatively, $C D_{{ }^{+}} T$ lymphocytes will become $T$ helper lymphocytes, each of which specialised for particular tasks.