Volker Lenhard

Blood transfusion-induced suppression of cellular immunity in man

The effect of planned blood transfusions on cell-mediated immunity was studied in previously nontransfused prospective kidney graft recipients. Following transfusion of washed erythrocytes a marked suppression of cellular immunity was found, indicated by reduced response to mitogenic (PHA, Con A, PWM) and antigenic stimulation (Ag-C containing PPD, tetanus toxoid, streptolysin, mumps, vaccinia antigen). A second transfusion led to a more pronounced and prolonged immunosuppression. No suppression was found when autologous blood was applied to volunteers. Preliminary results show autologous and allogeneic MLR suppression when mitomycin-C treated patient cells taken after transfusion are added. Our findings indicate that blood transfusion-induced suppression of cell-mediated immunity might be caused by an unspecific suppressor cell.

Human leucocyte antigens in idiopathic nephrotic syndrome in children

An association of the idiopathic nephrotic syndrome (NS) with certain human leucocyte antigens (HLA) has been reported repeatedly. The aim of this study is to characterize further the clinical and histological features of patients with NS in relation to their HLA phenotypes. HLA antigens were determined in 132 paediatric patients with NS. In 91 steroid-sensitive patients (usually associated with minimal glomerular changes), the antigen frequencies of HLA-DR3, HLA-DR7, and HLA-B8,-DR3 combined were significantly increased compared with controls. The strongest association was observed with the combined occurrence of HLA-B8,-DR3,-DR7 (relative risk 21.5). This association and that with HLA-DR3 alone were strongest in the presence of frequent relapses and steroid dependence compared with children without or with infrequent relapses. The pattern of HLA antigens was similar in the 57 steroid-sensitive patients with biopsy-proven minimal glomerular changes. In 41 children with steroid-resistant NS (usually associated with focal segmental glomerulosclerosis) a similar trend for increased antigen frequencies was found but the data were significant only for the combined occurrence of HLA-B8,-DR3 and-DR7. In all patients combined the frequency of the HLA associations was significantly lower when the age of onset was greater than 8 years compared with that of younger patients. It is concluded that the immunogenetic background of the steroid-sensitive and steroid-resistant NS is different and age-dependent.

Suppression of antibody response and prolongation of skin graft survival by multiple blood transfusions in the rat.

The effect of blood transfusions (BT) on antibody response and skin graft survival was studied in the strongly MHC-incompatible BN and LEW combination. One-to-three BT induced high titer antibodies. Additional BT, however, led to a decrease of antibody titers. After 15 BT the recipients either had no detectable antibodies, or they had very low antibody titers. This suppression of response was shown to be distinct from a simple loss of antibody activity caused by lack of further antigenic challenge. In multiple transfused rats, humoral nonreactivity persisted in spite of rechallenge with antigen; in animals that lost their antibodies as a result of lack of further stimulation, an additional BT boosted strong antibody production. In LEW recipients of multiple BN transfusions, not only the specific anti-BN response but also reactivity to third-party BUF blood was suppressed. However, whereas the donorspecific response (anti-BN) was largely inhibited after a ten-week interval, the response to third-party BUF blood recovered. The state of humoral nonreactivity could be transferred by spleen cells to nontransfused syngeneic animals. In LEW rats that received three injections of 5 x 107 “suppressor” spleen cells, the antibody response to BN blood was strongly impaired as compared with animals that received normal spleen cells. BN or (BNxLEW)F1 skin grafts survived significantly better in multiple transfused LEW rats than in nontransfused controls. This was even more pronounced when ALS was given additionally. Third-party grafts (BUF) survived only slightly better than controls. It is concluded that multiple BT (1) result in humoral anti-donor nonreactivity secondary to an initial antibody response, (2) induce strong specific and weak nonspecific suppressor cell activity, and (3) increase skin graft survival.

A rapid screening technique for lymphocytotoxic antibodies using Tray-frozen lymphocytes

A method whereby sera can be screened for the presence of lymphocytotoxic antibodies within 4 hr using lymphocytes frozen in microtest trays is described. The reactions of the sera of 48 hemodialysis patients against freshly prepared lymphocytes were compared with those against tube-frozen (384 reaction pairs) and tray-frozen (864 reaction pairs) cells. There was a better than 90% concordance, and only 3% of the reactions differed from negative to strongly positive or vice versa. Preliminary results indicate that the method is also suitable for B-cell (HLA-DR) antibody testing. Routine screening against 50- or 100-cell panels can be accomplished more rapidly and more efficiently using tray-frozen lymphocytes. The data matrix for analysis of a serums HLA specificity is greatly reduced in comparison to the conventional screening technique, rendering the method particularly suitable for microcomputer processing.

Chemotactic activity of lectins in vitro.

The effects of concanavalin A (Con A) and leucoagglutinin (LA) on the locomotor response of phagocytes have been studied in vitro. At concentrations of 1 to 4 microgram/mol, Con A and LA induced maximal chemokinesis and chemotaxis of monocytes, macrophages and, to a lesser degree, also of neutrophils. The lectin-induced locomotion was accompanied by membrane alterations and metabolic changes, as shown by an increase of the 3H-uridine uptake and a rise of the hexose monophosphate shunt activity. The chemotactic activity of Con A was inhibited by alpha-methyl mannoside (50 mM) or by pretreatment of the cells with trypsin. These data indicate that lectins such as Con A induce chemotaxis by a specific binding to receptors of the cell membrane. It is suggested that bivalent ligand binding is required as a signal to elicit chemotactic locomotion.

The effect of dialysate magnesium concentration on serum PTH-levels in patients on maintenance haemodialysis

SummaryAn inerease of dialysate magnesium concentration from 1.5 mval/l to 2.5 mval/l did not reduce significantly i PTH levels in haemodialysed patients, dialysed against 3.5 mEq Ca/l in the dialysate. Thus, when sufficiently high Ca concentrations in the dialysate are used, no further reduction of serum PTH levels is seen by elevating Mg in dialysate.ZusammenfassungDie Erhöhung der Dialysat-Magnesium-Konzentration von 1,5 mval/l auf 2,5 mval/l bei Verwendung einer Dialysat-Calcium-Konzentration von 3,5 mval/l führte zu keiner signifikanten Reduktion der radioimmunologisch gemessenen Serum-Parathormonspiegel. Bei ausreichend hohen Dialysat-Calcium-Konzentrationen bewirkt somit die Erhöhung der Dialysat-Magnesiumspiegel keine weitere meßbare Reduktion der PTH-Ausschüttung.

The Lewis antigen system and its relevance for clinical transplantation.

The influence of the Lewis blood group system on transplant survival was studied retrospectively in 161 kidney transplantations. Le (a-b+) recipients had significantly higher graft survival rates than Le (a+b-) or Le (a-b-) recipients. From the known distribution of the Lewis blood groups among the European population, a high percentage of Lewis-compatible transplants would be expected among Le (a-b+) recipients in contrast to the Le (a+b-) and Le (a-b-) recipients. Other factors which are known to influence transplant prognosis such as HLA-match between donor and recipient, ischemic time of the transplants and pretransplant blood transfusions did not differ significantly in any of the three groups studied. Our data again suggest the relevance of the Lewis blood group system for clinical kidney transplantation. The findings should be confirmed by prospective typing of donor and recipient for Lewis antigens.

Recent perspectives on the mechanisms of rejection in kidney transplantation

Today, the success of kidney transplantation largely depends upon immunological factors. Despite the fact that the results of clinical transplantation have continuously improved within the last years, graft rejection is still a relatively frequent event. The fate of a transplant is primarily dependent upon differences in the histocompatibility antigens between donor and recipient. These differences are responsible for the intensity of the immunological reaction. After transplantation there is an activation of T- and B-lymphocytes in the recipient. In cooperation with a subpopulation of T-lymphocytes, the T-helper cells, cytotoxic effector cells are generated from a further subpopulation of T-lymphocytes. In addition, amplifier mechanisms of cellular and humoral immunity are activated in the course of a rejection reaction. Sensitized lymphocytes may secrete mediators which concentrate the non-spezific cells such as monocytes, granulocytes and lymphocytes in the transplant and lead to the functional activation of these effector cells. The activation of B-lymphocytes leads to maturation of antibody secreting plasma cells. Antibodies cause cytotoxic damage to the transplant, either with involvement of the complement system or through cells which produce antibody-dependent cytotoxicity. On the other hand, blocking antibodies, immune complexes or suppressor lymphocytes may have a protective effect on the transplant. The aim of this paper is to describe the present state of knowledge of these diverse mechanisms, their mutual interactions as well as their relevance for clinical transplantation. It is expected that a better understanding of the immune reactions involved will influence the diagnostic as well as the therapeutic procedures used in patients with graft rejection, thus leading to better results for kidney transplantation in the future.SummaryToday, the success of kidney transplantation largely depends upon immunological factors. Despite the fact that the results of clinical transplantation have continuously improved within the last years, graft rejection is still a relatively frequent event. The fate of a transplant is primarily dependent upon differences in the histocompatibility antigens between donor and recipient. These differences are responsible for the intensity of the immunological reaction. After transplantation there is an activation of T- and B-lymphocytes in the recipient. In cooperation with a subpopulation of T-lymphocytes, the T-helper cells, cytotoxic effector cells are generated from a further subpopulation of T-lymphocytes. In addition, amplifier mechanisms of cellular and humoral immunity are activated in the course of a rejection reaction. Sensitized lymphocytes may secrete mediators which concentrate the non-spezific cells such as monocytes, granulocytes and lymphocytes in the transplant and lead to the functional activation of these effector cells. The activation of B-lymphocytes leads to maturation of antibody secreting plasma cells. Antibodies cause cytotoxic damage to the transplant, either with involvement of the complement system or through cells which produce antibody-dependent cytotoxicity. On the other hand, blocking antibodies, immune complexes or suppressor lymphocytes may have a protective effect on the transplant. The aim of this paper is to describe the present state of knowledge of these diverse mechanisms, their mutual interactions as well as their relevance for clinical transplantation. It is expected that a better understanding of the immune reactions involved will influence the diagnostic as well as the therapeutic procedures used in patients with graft rejection, thus leading to better results for kidney transplantation in the future.ZusammenfassungDer Erfolg einer Nierentransplantation ist heute weitgehend von immunologischen Faktoren abhängig. Obwohl die Ergebnisse der klinischen Transplantation in den letzten Jahren zunehmend verbessert werden konnten, kommt es immer noch relativ häufig zur Abstoßung von Transplantaten. Das Schicksal eines Transplantats wird in erster Linie durch Unterschiede in den Histokompatibilitäts-Antigenen zwischen Spender und Empfänger bestimmt, die für die Stärke der immunologischen Reaktion verantwortlich sind. Nach der Transplantation kommt es im Empfänger zur Aktivierung von T- und B-Lymphozyten. Aus einer Subpopulation sensibilisierter T-Lymphozyten werden in Kooperation mit einer weiteren Subpopulation von T-Lymphozyten, den T-Helfer-Zellen, zytotoxische Effektorzellen generiert. Außerdem werden im Verlauf einer Abstoßungsreaktion Verstärkermechanismen der zellulären und humoralen Immunität ausgelöst. Von sensibilisierten Lymphozyten können Mediatoren sezerniert werden, die unspezifische Effektorzellen wie Monozyten, Granulozyten und Lymphozyten im Transplantat konzentrieren und zu ihrer Funktion aktivieren. Die Aktivierung von B-Lymphozyten führt zur Ausreifung Antikörper-sezernierender Plasmazellen. Antikörper können unter Komplementbeteiligung eine zytotoxische Schädigung des Transplantats verursachen oder Zellen zur sog. Antikörper-abhängigen Zytotoxizität befähigen. Andererseits können blockierende Antikörper, Immunkomplexe oder auch Suppressor-Lymphozyten einen protektiven Einfluß auf das Transplantat haben.Ziel dieser Arbeit ist es somit, diese vielfältigen Mechanismen, ihre Interaktion sowie Bedeutung für die klinische Nierentransplantation darzustellen. Es ist zu erwarten, daß das wachsende Verständnis in die Vorgänge bei der Abstoßungsreaktion das diagnostische und therapeutische Vorgehen beeinflußen wird und somit die Ergebnisse der Nierentransplantation in Zukunft verbessert werden können.