M.K. had been diagnosed with a particular variant of severe combined immunodeficiency (acronymed SCID), in which both B cells (white cells that make antibodies) and T cells (that kill microbially infected cells and help mount an immune response) are dysfunctional. A grotesque English garden of microbes—some common, some exotic—grew out of his blood: Streptococcus, Staphylococcus aureus, Staphylococcus epidermidis, weird fungal varieties, and rare bacterial species whose names I could not even pronounce. It was as if his body had been transformed into a living petri dish for microbes.
