The present invention relates to, among others, an in vitro method of modifying a cell graft containing immune cells comprising the steps of incubating a cell graft containing immune cells with an anti CD4 antibody wherein said incubating is carried out for from 1 minute to 7 days, b) removing unbound antibody from said graft； as well as to corresponding modified grafts and uses. The invention further relates to the modification of antibodies reactive to the CD4 human leukocyte antigen to provide anti-CD4 antibodies that have a reduced number of potential T-cell epitopes but retain the ability to bind to CD4, such as to an anti human CD4-antibody comprising a heavy chain immunoglobulin variable domain (VH) and a light chain immunoglobulin variable domain (VL), wherein at least one T cell epitope located outside the CDRs of said immunoglobulin variable domains is removed from said immunoglobulin variable domains. Preferably, the specificity and mode of action of the anti-CD4 antibodies are not affected by the modification(s).
