Diversity in the B cell and T cell repertoire.

Diversity in the B cell and T cell repertoire.
a) As a member of a research team studying a tribe found in a remote region of New Guinea, you make the astonishing discovery that they have only two variable (V) genes for the light (L) chain and three V genes for the heavy (H) chain of immunoglobulins. Nevertheless, they seem healthy and able to resist the diversity of pathogenic organisms endemic to the area. Suggest how this might be accomplished.
b) Individuals frequently harbour auto-reactive B cells (i.e. B cells that express receptors that recognise self-antigen), but do not develop autoimmune disease. Explain how this situation can occur.