Cross-reactivity refers to the action of antibodies. Cross-reactivity arises because antibodies aren't always 100% specific for their antigens.

Say gluten has the molecular appearance of an elephant - a trunk, 4 stocky legs, a tail, etc... when our bodies produce antibodies that recognize gluten, they may only produce an antibody that recognizes one part of gluten. Perhaps just tail, leg, or trunk. If you made the antibody against the trunk, you'll have a very specific antibody, as no other animals have trunks. If you made an antibody against the stocky leg, you might also react with something like a rhino. Or an antibody against the tail, might also recognize all sorts of other animal tails.

All gluten antibodies are not necessarily the same. Some may be more or less specific than others. It all depends on what molecular feature the antibodies recognize. Some are specific to gluten, others may be similar between various proteins. This explains why some gluten-intolerant folks cannot eat corn, but some can. Some can eat rice, but others cannot. Some react against casein, but others tolerate casein just fine.

Cross-reactivity also explains why leaky gut causes auto-immunity. You might create antibodies against wheat that also recognize your thyroid or pancreas, your body then initiates an immune response against your thyroid or pancreas.

So yes, what the doctor is saying is true: cross-reactivity might continue causing problems even when you eliminate what you're sensitive to. Of course, how do one know if you're simply cross reacting to corn due to a wheat sensitivity or you're simply also sensitive to corn primarily. That probably requires some antibody testing and blood work, though I don't know anything about that.

This is an older explanation but it does talk about those people who may react in the same way to both Rice and Corn, it's an older article so take it with a grain of salt...gluten free salt of course :-p

http://wheat.pw.usda.gov/ggpages/topics/Celiac.vs.grains.html

Truth

Yeah there is absolutely cross-reactivity between gluten and corn, as well as gluten and other things. I'm not at home so I don't have the papers handy, but google gluten and maize and you'll find some things. Cross-contamination can occur during processing, or in a fryer, in a kitchen, etc.

Gluten intolerance and gluten allergy are also different, as they relate to different types of reactions (IgG vs IgE, etc)

Yes, there can be a cross-reaction or rather additional reactions to grain proteins among Celiac's and the gluten intolerant. I happen to be one of those people who react to multiple grains. It's not that uncommon.

Here's some background: http://alternativethyroidtherapy.com/wp-content/uploads/2011/07/Gluten-cross-reactive-foods.pdf

And http://blog.primohealthcoach.com/blog/bid/79586/18-Gluten-Cross-Reactive-Foods

Celiac's is typically gene related, an autoimmune reaction to gluten grains that is triggered by exposure to gluten. Not everyone with the genes (30 percent of the population) develop the disorder. It can be triggered early in childhood or late in life, but once triggered there's no reversing it. Such individuals (like me) need to remain gluten-free forever.

Cross-reactions to other foods however may either increase or subside over time because it's the immune system over-reacting to proteins that are similar to gluten. Statistically about half of all Celiac's are also reactive to casein, a dairy protein. A significant number of Celiac's do not see comlete healing on a GF diet probably due to the problems both with cross contamination and with cross reaction. In the former the person is accidentally ingesting gluten. In the latter the autoimmune system is accidentally reacting to something it shouldn't.

Basically, after following a Paleo diet for a couple of years it's been much easier to sort out cross-reactions and if you are strict it also eliminates the cross contamination issue. I believe a strict Paleo diet is an ideal diet for healing the damage caused by gluten - or at least it has been for me.

It's astonishing to me the number of Celiac's who try to combat their 'disorder' by trying to duplicate the SAD diet with alternative grains. It's only a disorder or 'illness' if I continued to eat gluten/grains. Eating grain-free isn't a 'new' concept. Paleo is just the latest version, and a very handy one, too.