Camel Antibodies are Strange

I mentioned in class that camel antibodies are heat-resistant, and someone has developed a camel antibody-based dip-stick test for caffeine in hot drinks (see Nature, 11 May 2006, p.169). Becky Buckley told me afterwards that camel Abs are structurally odd, so I did some reading, and find that a majority of them have no L chains, but are H chain dimers! So the MW is more like 100,000 than 150,000. In human Abs, it's hard to get 2 H chains to dimerize, because their association surfaces (part of the V region framework) are "looking" for L chains. So some clever types have "camelized" human H chains, mutating the amino acids that repel other H chains, and successfully made H chain dimers, some of which are biologically active. Nature and biotechnology, aren't they both lovely?