Background

Passenger lymphocyte syndrome (PLS) is a typical complication of solid organ or hematopoietic stem cell transplantation (HSCT). It is caused by donor-derived B-lymphocytes producing antibodies to antigens on the recipient's red blood cells, which can lead to hemolysis or even graft failure. PLS is considered rare, but the true incidence is unknown because many cases go undetected. We report three cases of PLS at our institution.

Methods

One patient each was studied after HSCT, donor lymphocyte infusion (DLI) and after heart-lung transplantation. All three patients were diagnosed with PLS by serological abnormalities or unexplained antibodies during routine blood bank testing.

Serological studies including antibody screening test in the indirect antiglobulin test (IAT) and papain test, as well as direct antiglobulin test (DAT) were performed using the standard gel technique (Biorad, Cressier sur Morat, Switzerland and Grifols, Barcelona, Spain). Red blood cell (RBC)-bound antibodies were eluted using the acid method (BAG, Lich, Germany).

Results

The clinical and serological data of the patients are shown in Table 1. PLS occurred between 10 and 20 days following transplantation. Patients 1 and 2 developed hemolytic anemia (Hb minimal 6.2 / 8.8 g/dl and LDH 1664 / 431 U/l, respectively and haptoglobin below detection limit), but only patient 1 needed therapy (RBC transfusion, i.v.Ig, prednisolone). Patient 3 had already changed to the donor's blood group (A RhD-) before transfusion of the DLIs, therefore hemolysis did not occur. Of the irregular RBC antibodies, only the donor anti-D from patient 1 was known before transplantation. In patient 2, the PLS was noticed mainly by a positive crossmatch with RBCs of type B, anti-B on the recipients RBCs and a negative antibody screening test

Conclusion

The diagnosis of PLS can be difficult, and the clinical and serologic picture varies. PLS typically presents 2-3 weeks following transplantation with or without hemolysis in combination with a (newly diagnosed) positive DAT and/or detection of antibodies against the recipient"s blood type. The latter must not be confused with autoantibodies as they are donor-derived alloantibodies, and antigen-negative blood must be provided in cases of anemia requiring transfusion.

Offenlegung Interessenkonflikt:

The authors declare no conflicts of interest