Xenotransplantation and ABO incompatible transplantation: the similarities they share.

Transplantation of kidney allografts across the ABO barrier has been feasible with the development of technologies for removal of anti-blood group antibodies from the circulation of the recipent. The recipients of ABO incompatible grafts display tolerance, accommodation or rejection of the graft. Understanding the factors that determine the outcome of the immune response against incompatible blood group antigens has required the study of an appropriate experimental animal model. The model used is that of knockout (KO) mice for the alpha1,3galactosyltransferase gene, lacking the alpha-gal epitopes and transplanted with wild type mouse heart expressing the alpha-gal epitope. The alpha-gal epitope (Galalpha1-3Galbeta1-(3)4GlcNAc-R) is one of the most abundant carbohydrate epitopes on cells of non-primate mammals and New World monkeys, where it is synthesized by the glycosylation enzyme alpha1,3galactosyltransferase. In humans, apes and Old World monkeys, this epitope is absent due to an evolutionary event that led to the inactivation of the alpha1,3galactosyltransferase gene in ancestral Old World primates. Instead, humans, apes and Old World monkeys produce a natural antibody, the anti-Gal antibody, that is the most abundant natural antibody in humans (approximately 1% of circulating immunoglobulins) and which specifically interacts with alpha-gal epitopes. The interaction between anti-Gal and alpha-gal epitopes is a major immunologic barrier in xenotransplantation, preventing transplantation of pig organs or tissues (i.e. xenografts) into humans. Anti-Gal antibodies also comprise a large proportion of anti-blood group B activity in A and O individuals. Moreover, in recipients of ABO incompatible grafts, much of the elicited anti-A and anti-B antibodies are in fact anti-Gal antibodies capable of binding also to the incompatible blood group antigens. Since the alpha-gal epitope is very similar in its structure to blood groups A and B, understanding anti-Gal response to alpha-gal epitopes is likely to provide information on the immune response to ABO incompatible antigens. Studies on the immune response to alpha-gal epitopes in KO mice have indicated that this epitope can not activate T cells. Anti-Gal B cells engaging alpha-gal epitopes on transplated wild type mouse heart can be activated to produce their antibodies only if they receive help from T cells that are activated by allogeneic or xenogeneic peptides. If T cell help is not available for several days the B cells are induced to differentiate into cells capable of producing accommodating antibodies. Accommodating anti-Gal antibodies bind to the incompatible carbohydrate antigen but do not induce rejection. Prolonged exposure of anti-Gal B cells to the incompatible alpha-gal epitope on the wild type mouse heart graft induces tolerance due to the deletion of these B cells. These studies imply that similar variation in the availability of T cell help in recipients of ABO incompatible grafts result in rejection, accommodation or tolerance, to the blood group antigen. The studies on immune response to incompatible alpha-gal epitopes have further indicated that tolerance to incompatible blood group antigens can be achieved by gene therapy with autologous bone marrow cells or autologous lymphocytes engineered to express the incompatible blood group antigen. Studies in the mouse model suggest that administration into the patient such autologous cells engineered to express the incompatible transplantation carbohydrate antigen induces deletion of anti-blood group B cells and induction of tolerance, provided that the anti-blood group antibodies are removed. Such tolerance is perpetuated indefinitely by the subsequent transplantation of the organ expressing the incompatible blood group antigen.

Can blood group O red cells of donor origin acquire weak group A reactivity through serum A transferase of the recipient after bone marrow transplantation?

BACKGROUND: Blood group A substance was detected on red cells of a patient who received a bone marrow transplant from a blood group O donor 3.5 years ago. MATERIALS AND METHODS: Peripheral blood was investigated by conventional serological techniques, fluorescence in situ hybridisation, and polymerase chain reaction. RESULTS: All peripheral blood cells are of donor origin. Anti-A and not anti-A, B of blood group O individuals can be absorbed to the group O red cells of the patient. CONCLUSION: We suppose that the patient's residual serum A transferase attaches the appropriate sugar to substance H on the red cell membrane to form substance A.

Identification of an anti-A and anti-B blood group glycosyltransferase antibody after incompatible bone marrow transplant.

The occurrence of a potent antibody against plasmatic A and B glycosyltransferase activities has been characterized in a patient (blood group A1) transplanted with a bone marrow from a blood group O donor. A and B glycosyltransferases were purified to near homogeneity from plasma of A1 and B blood-group individuals. The half-maximal inhibition of both enzymes was obtained at 1 to 2 micrograms/mL of the post-transplant IgG fraction, prepared by protein A-sepharose chromatography. A and B glycosyltransferases were also recognized by the post-transplant IgG fraction after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by electrophoretic transfer to nitrocellulose membranes.

Presence of antibody to A- and B-transferases in minor incompatible bone marrow transplant.

The contribution of the bone marrow to plasma A- or B-transferase activities has been studied in patients who underwent incompatible bone marrow transplantation (BMT). As deduced from major incompatibility (group O recipient/A donor), the contribution of the marrow to these plasma activities was c. 5-10% of the total activity. In cases of minor incompatible transplants (A recipient/O donor), normal plasma activity was present in two patients, while no activity was found in a further two in whom a potent antitransferase was detected. The antibody inhibited both A- and B-transferase activities to a high titre. The patients in whom this antibody arose exhibited severe graft-versus-host disease.

Presence of an inhibitor of glycosyltransferase activity in a patient following an ABO incompatible liver transplant.

The contribution of the liver to plasma ABO glycosyltransferase activity has been studied in a group O individual transplanted with a liver from a group B donor. The B transferase activity present in the post-transplantation plasma was negligible. However, a potent B transferase inhibitor, absent from the pretransplantation plasma, was present after transplantation. The inhibitor was present in the excluded fraction following Sephadex G-25 gel filtration, but was retained by a protein A-Sepharose column, suggesting that it was an IgG antibody. This inhibitor was also effective in reducing A transferase activity.

Incompatible A antigen expressed in tumors of blood group O individuals: immunochemical, immunohistologic, and enzymatic characterization.

Monofucosyl type 1 chain A (type 1 Aa) and difucosyl type 1 chain A (ALeb), but not other types of A antigens, have been detected by application of carrier type-specific monoclonal anti-A antibodies (AH21 and HH3) in colonic tumors of blood group O individuals. An A-transferase activity (UDP-Gal-NAc:H-alpha-GalNAc transferase) was demonstrated in the extract of one of the O tumors expressing A antigen. The incidence of A antigen expression in O tumors was found to be two out of 15 cases, based on TLC immunostaining of glycolipid extracts, and five out of 50 cases, based on immunofluorescent staining of tumors with AH21 and HH3 antibodies.

Relationship between human serum placental alkaline phosphatase and the ABo and Rh compatibility status in pregnancy.

458 unrelated healthy women at various gestational ages were examined for serum heat-stable alkaline phosphatase (HSALP) activity. The sample was subdivided into four groups according to the compatibility mating type in the ABO and Rh systems: double compatible, ABO incompatible, Rh incompatible and double incompatible. The results confirm the exponential growth of serum placental isoenzyme as a function of gestational age and show that the moment of appearance of the placental isoenzyme is six weeks earlier in double incompatible matings.

Caesarean section in a patient with low serum cholinesterase activity following plasmapheresis. A case report and review.

Plasmapheresis has been used in the control of rhesus incompatibility in pregnancy, resulting in a marked reduction in serum cholinesterase activity. A number of these patients will subsequently require anaesthesia and hence be at risk from suxamethonium sensitivity. A caesarean section was performed on a 26-year-old patient with this condition. The pre-operative preparation and anaesthetic management are presented and the specific problems discussed.

[Activities of peroxidase, alkaline phosphatase, and lactatedehydrogenase in amniotic fluid in normal and pathologically affected pregnancy (author's transl)]. / Zur Aktivität von Peroxidase, alkalischer Phosphatase und Laktatdehydrogenase im Fruchtwasser bei normal und pathologisch verlaufenden Schwangerschaften.

Reported in this paper are measurements of peroxidase as well as of alkaline phosphatases, both stable and labile to heat, and of lactatedehydrogenase in amniotic fluid. Included in the investigations reported were cases of normal pregnancy, pregnancy with low-weight infants, gestoses, and Rh incompatibility. The above enzymes proved unsuitable for assessment of foetal condition, as may be seen from the results. Identification of pregnancy age below 30 weeks was found to be possible by peroxidase determination.

Acid- and alkaline phosphatase in amniotic fluid in normal and complicated pregnancy.

171 samples of amniotic fluid were obtained by abdominal amniocentesis from 67 women with complicated pregnancies (isoimmunization, diabetes mellitus or toxaemia). The levels of heat-labile alkaline phosphatase (HLAP), heat-stable alkaline phosphatase (HSAP) and acid phosphatase (AcP) were determined and compared to the enzyme levels in 179 samples from women with normal pregnancies of corresponding gestational ages. HLAP showed two "peaks" of activity, one in the 5th-22nd week and the other at term. HSAP and AcP showed increased activity at term. HSAP was decreased (p less than 0.01) in isoimmunization between the 36th and 40th week. 11 cases of toxaemia with placental insufficiency showed no differences in the levels of HLAP and HSAP compared with normal pregnancy. AcP showed no differences between normal and complicated pregnancy. Samples contaminated by blood showed no significant increase in the acid- and alkaline phosphatase levels. Samples contaminated by meconium showed a complex pattern. Some samples had normal enzyme levels, some had high levels of HLAP only and some had high levels of HSAP and AcP. The origin of the enzymes is not known with certainty. HSAP in amniotic fluid is most likely not of placental but intestinal origin. Determinations of acid- and alkaline phosphatase in amniotic fluid seem to be of little values in the clinical management of complicated pregnancy.