Reduced folate carrier polymorphism determines methotrexate uptake by B cells and CD4+ T cells.
OBJECTIVE
To examine if polymorphism 80G --> A in the Reduced Folate Carrier (RFC) affects uptake of MTX in B- and CD4+ T-cells.


METHODS
Mononuclear cells were isolated from peripheral blood of healthy persons. Real-time PCR was used to detect the RFC80 variants. FITC-labelled MTX was added to cells stimulated with Candida albicans or tetanus toxoid, and the uptake of MTX was measured by flow cytometry. A FITC-conjugated monoclonal antibody against RFC was used to detect the cellular RFC expression.


RESULTS
Antigen-stimulated CD4+ T cells and B cells from individuals with the GG variant (n = 9) exhibited lower uptake of MTX than individuals expressing the AA variant (n = 8), or the GA variant (n = 8). No difference could be demonstrated between the three groups with respect to the expression of RFC by CD4+ T cells and B cells, and CD4+ T cells from individuals homozygous for the G allele exhibited lower uptake of MTX per receptor than CD4+ T cells from individuals homozygous for the A allele.


CONCLUSIONS
MTX is taken up more efficiently via the A allele than via the G allele. This difference between the variant forms of RFC suggests that genotyping could be relevant for determining the relevant dosage of MTX in the treatment of neoplastic and autoimmune disease.
Baslund
B
B
Department of Rheumatology, Rigshospitalet and the University of Copenhagen, Denmark. bbaslund@gmail.com
Gregers
J
J
Nielsen
C H
CH
D000946:Antigens, Fungal / Q000276:immunology; D018501:Antirheumatic Agents / Q000097:blood; D001402:B-Lymphocytes / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D002176:Candida albicans / Q000276:immunology; D002478:Cells, Cultured; D005838:Genotype; D006801:Humans; D008213:Lymphocyte Activation; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008727:Methotrexate / Q000097:blood*; D011110:Polymorphism, Genetic; D058978:Reduced Folate Carrier Protein; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism; D013745:Tetanus Toxoid / Q000276:immunology
D000946:Antigens, Fungal; D018501:Antirheumatic Agents; D026901:Membrane Transport Proteins; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D013745:Tetanus Toxoid; D008727:Methotrexate