Certainly. <img src="i/expressions/face-icon-small-smile.gif" border="0">
There are, as was briefly mentioned, Classes I, II, III, IV, and V. Class I is the worst. Class V is the mildest. Delta F508 (which is indeed the most common CF gene in the United States --- it's not the same everywhere else... I know the most common in Israel is w1282x) is a Class II. It's not quite as simple as "Class I is the worst" even though that's the basic trend. They are put in different Classes based on what exactly the malfunction in the gene is.
Class I: Defective protein production with premature termination of CFTR production. Class 1 mutations produce few or no functioning CFTR chloride channels
Class II: Defective trafficking of CFTR so that it does not reach the apical surface membrane where it is intended to function
Class III: Defective regulation of CFTR even though it is able to reach the apical cell surface
Class IV: CFTR reaches the apical surface but conduction through the channel is defective
Class V: Associated with reduced synthesis of functional CFTR
(Source: <a target=_blank class=ftalternatingbarlinklarge href="http://www.cysticfibrosismedic...CFdocs/CFText/gene.htm">http://www.cysticfibrosismedic...CFdocs/CFText/gene.htm</a> )
Everything in this following paragraph is simply my interpretation of that information above, in easier to understand terms. I may be a little off in explaining them, so don't quote me. If anyone understands it better, feel free to correct me where necessary.
The CFTR stands for Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). It's basically a channel between cells that doesn't work right in CFers. Class I, in lamen's terms, as it says above, produce no or few CFTRs. Class II has CFTRs but they don't travel to the right places, Class III has CFTRs, and they get to the right place, they're just not 100% functional. Class IV the CFTRs are there, they get to the right place, and they work well, but the channel creates a problem. And Class V has CFTRs that function correctly, just not all the time (basically, they have some working ones and some not).
As you can see, the descriptions of the defect get milder as the Class number gets higher. You go from "no CFTRs" in a Class I, to "sometimes they don't work" in a Class V. Big difference.
