Because of the complementary roles of the these two genes, a protective Factor B variation can protect against AMD, even if one carries a risk-increasing variant of Factor h, and vice versa.

To prove that factor a has no effect whatever on outcome b may be important in the sense that it refutes a hypothesis.

The team discovered that a certain B. subtilis signalling molecule, known as competence and sporulation factor (CSF), is detected by human gut cells (Cell Host &Microbe, vol 1, p 299).