Raised immunoglobulin A and circulating T follicular helper cells are linked to the development of food allergy in paediatric liver transplant patients

Summary Background Post‐transplant food allergy ( LTFA ) is increasingly observed after paediatric liver transplantation ( LT ). Although the immunopathology of LTFA remains unclear, immunoglobulin (Ig) E seems to be implicated. Objective To study humoral and cellular immunity in paediatric LT patients in search for factors associated with LTFA , and compare with healthy controls ( HC ) and non‐transplant food‐allergic children ( FA ). Methods We studied serum Ig levels in 29 LTFA , 43 non‐food‐allergic LT patients ( LT no FA ), 21 FA patients and 36 HC . Serum‐specific IgA and IgE against common food allergens in LTFA , IgA 1 , IgA 2 and joining‐chain‐containing polymeric IgA ( pIgA ) were measured. Peripheral blood mononuclear cells were analysed by flow cytometry for B and T cell populations of interest. Results Serum IgA and specific IgA were higher in LTFA compared to LT no FA . LTFA patients had the highest proportion of circulating T follicular helper cells ( cT fh). The percentage of cT fh correlated positively with serum IgA. Unique in LTFA was also the significant increase in serum markers of mucosal IgA and the decrease in the Th17 subset of CXCR 5 − CD 4 + cells compared to HC . Both LT patients exhibited a rise in IgA + memory B cells and plasmablasts compared to HC and FA . Conclusions LT has an impact on humoral immunity, remarkably in those patients developing FA . The increase in serum markers of mucosal IgA, food allergen‐specific IgA and cT fh cells observed in LTFA , point towards a disturbance in intestinal immune homoeostasis in this patient group.