Writing as somebody whose day job includes immunology and apologies if this is a bit technical:

Gs221 is a variant (an allele) of a protein called HLA-DQ2. The HLA proteins occur in two general forms - Class I and Class II. Class I HLA proteins are important in helping the immune system to take care of virus infections.

Class II HLA proteins (like HLA-DQ2) have a different job. They present fragments (peptides) made by pathogens to a class of cells called helper T cells. When that happens helper T cells get activated - they can help B cells, which make antibodies, and other kinds of T cells to get rid of the pathogen which made the peptide - this is a good thing.

However, sometimes the immune system makes a "mistake" - a normal peptide, from a protein made by healthy body cells, on a specific Class II HLA allele, can "trick" helper T cells into "thinking" that peptide came from a pathogen - this mistake is the basis of most auto-immune diseases, including coeliac disease. Type I diabetes (probably the most common auto-immune disease) is another example - alleles of many Class II HLA proteins are known risk factors for it.

I hope that this is not too confusing.

The important message is that genetics is not destiny - just because you have inherited Gs221 does not mean that you are doomed to coeliac disease - your health professional care team should be able to advise you about this.

All the best.