As humoral responses progress, the average affinity of the antibodies produced rises, in a process known as "affinity maturation." This seems at odds with at least one aspect of the clonal selection hypothesis, since the notion of "clonal integrity" implies that the progeny of an activated lymphocyte retain the specificity the original, pre-immune, antigen receptor. So here are the questions:

What is the basis for "affinity maturation" in humoral responses?

Does this contradict the tenets of clonal selection? Perhaps a bit more broadly, does this force rejection of the clonal selection hypothesis as a viable model to explain the cellular basis for specificity of adaptive immunity?

At the end of the response, you should raise an issue you are curious about related to the topic in the question.