Tolerance and hematopoietic stem cell transplantation 50 years after Burnet's theory.

OBJECTIVE: In 1949, the original formulation of Burnet's theory on the mechanisms responsible for the capacity of the immune system to discriminate between foreign antigens (i.e., the "non-self") and the cells of its own body (i.e., the "self") was published. Since then, further refinements and reconsiderations of the basic concepts underlying the achievement of a state of tolerance toward a certain antigen have been reported. Here, we attempt to analyze critically new clinical and experimental strategies aimed at inducing alloantigen-specific unresponsiveness. DATA SOURCES: The data discussed in this review are drawn from articles and abstracts published in journals covered by the Science Citation Index and Medline. STATE OF THE ART: Induction of tolerance toward alloantigens still remains one of the most elusive goals of clinical immunology. Until now, nonspecific immunosuppressive drugs have been used to successfully perform both solid organ and hematopoietic stem cell transplantation. However, using this approach, patients given an allograft are exposed to the threat of infections, tumors, and other side effects. Moreover, in solid organ transplant recipients, permanent tolerance toward the graft's alloantigens is never achieved. Recently, considerable progress has been made in expanding our knowledge of transplant tolerance. The traditional model of central tolerance, derived from Burnet's concept, has been complemented by knowledge of mechanisms of peripheral tolerance. CONCLUSIONS: New experimental and therapeutic trials based on the blockade of costimulatory molecules, as well as on generation and infusion of either regulatory or nonimmunogenic cells, have been recently proposed for inducing alloantigen-specific tolerance.The achievements obtained in understanding the mechanisms of unresponsiveness toward non-self antigens are fundamental prerequisites for successful allogeneic transplants, and they could open a new exciting era of specific, immunosuppressive therapies.

Immunoglobulin G3-specific antibodies as a marker for early diagnosis of HIV infection in children.

Early diagnosis of HIV infection in the child of an HIV-infected mother may be difficult as HIV-specific immunoglobulin (Ig) G antibodies are transmitted to the fetus transplacentally. In an attempt to provide a new, simpler tool for early identification of HIV-infected children we analysed the HIV-specific IgG subclass pattern during the first year of life. One hundred and one samples were collected from 35 children born to HIV-seropositive mothers, among whom 18 seroreverted during follow-up and 17 were HIV-infected (two P1 and 15 P2 according to the Centers for Disease Control classification). Serum HIV-specific IgG3 was detectable at least in one sample in 26 out of 35 children. All 17 HIV-infected children showed persistently detectable specific IgG3, both with stable or progressive disease. Out of the 18 uninfected children who seroreverted during follow-up, nine were HIV-specific IgG3-negative when first tested and nine lost HIV-specific-IgG3 within 28 weeks after birth. The correlation of the serological results with clinical information and any other diagnostic tool on each child suggests that the clearance of specific-IgG3 antibodies heralds seroconversion in uninfected passive antibody-carrier children. This observation provides the basis for a new, simple and effective method for early diagnosis of HIV infection in children born to seropositive mothers.

Prevalence of primary adult lactose malabsorption and awareness of milk intolerance in Italy.

A total of 308 healthy Italian adults (192 females, 116 males; mean age 29.2 yr) were examined using a field version of the lactose tolerance test with breath hydrogen determination. Two geographical groups were formed according to the birth places of the probands' grandparents: 208 subjects from northern Italy (mainly from the regions of Piemonte, Lombardia, and Veneto) and 100 probands from Sicily. Lactose malabsorption was diagnosed in 106 subjects in group "north" (51%) and in 71 subjects in group "Sicily" (71%). Awareness of milk intolerance was more frequent in lactose malabsorbers. The incidence of diarrhea after the test dose of lactose was significantly higher in "aware" lactose malabsorbers, when compared with persons of the same group who had not experienced milk intolerance. The significant difference in lactose malabsorption frequency between northern Italy and Sicily is further evidence of a north-south gradient of lactase gene frequencies in Europe.

An enzyme-linked immunosorbent assay for cow's milk protein-specific IgE using biotinylated antigen. Avoidance of interference by specific IgG.

Detection of specific IgE by the radioallergosorbent test (RAST) which uses labelled antibody can be hampered by the presence of antibodies other than IgE but with the same specificity and may limit usefulness of the RAST for diagnosis of IgE-mediated milk allergy in infancy when high titres of cow's milk protein-specific IgG antibodies are known to be present. This can be avoided by using a system employing labelled antigen, such as the enzyme-linked immunosorbent assay (ELISA) described here, where IgE in the test serum is immunoadsorbed to anti-human IgE coated to microtitre plates. Biotinylated antigen, in this case cow's milk proteins, binds to specific IgE and the reaction is revealed colorimetrically by adding horseradish peroxidase (HRP)-avidin conjugate.

Transplant of bone marrow and cord blood hematopoietic stem cells in pediatric practice, revisited according to the fundamental principles of bioethics.

The two most widely used sources of hematopoietic stem cells for allogeneic transplants in pediatric practice are bone marrow (BM) and cord blood (CB). While bone marrow transplantation (BMT) is reaching its 30th year of application, human umbilical cord blood transplantation (HUCBT) is approaching its 10th. Although these procedures have basically the same purpose, a number of biological differences distinguish them. In particular, the intrinsically limited quantity of CB stem cells and their immunological naiveté confer peculiar characteristics to these hematopoietic progenitors. From a bioethical point of view, the problems which have repeatedly been raised when the BM donor is a child are well-known. Different but no less important ethical problems are raised when one considers HUCBT; in this regard the most important issues are the easier propensity of programming a CB donor in comparison with a BM donor (clearly due to the shorter time interval needed to collect the hematopoietic progenitors); the in utero HLA-typing; the implication of employing 'blood belonging to a neonate' for a third party; the need to perform a number of investigations both on the CB of the donor and on the mother and the implications that the discovery of disease may have for them, but also the need to establish banks for storing CB, with the accompanying administration and management problems. All these different aspects of UCBT will be discussed in the light of the four fundamental and traditional principles of bioethics, namely autonomy, nonmaleficence, beneficence and justice.

Allogeneic bone marrow transplantation in children from other than HLA-identical sibling donor.

Optimal allogeneic bone marrow transplantation (BMT) presupposes the use of a HLA-identical sibling as donor. Unfortunately, only about 30% of patients have an HLA-matched donor, so that the use of alternative donors has been increasingly used. We report an analysis of 13 children transplanted using an HLA-partially matched donor as source of haemopoietic stem cells. They suffered of ALL (3 pts), ANLL (1 pt), SAA (2 pts), Osteopetrosis (1 pt), Wiskott-Aldrich Syndrome (2 pts), Severe Combined Immunodeficiency Disease (2 pts) and Familial Haemophagocitic Lymphohistiocytosis (2 pts). Full engraftment was obtained in all 11 of the patients who survived longer than 14 days and, globally, a moderate incidence of acute GvHD (grade II-IV) was observed in the evaluable patients (3 out of 11 with a percentage of 27%); only a patient of the six survivors more than one hundred days after BMT had severe chronic GvHD (16.6%). Four pts (31%) are actually alive and well (mean follow-up 358 days) with a mean Karnofsky score of 95%. Our data suggest that BMT from HLA-partially matched donors could represent a possible alternative therapeutic strategy in children when a compatible donor is not available. This is especially due to the reduced severity of GvHD in childhood and because of T-cell depleted marrow transplants could obtain more satisfactory results when employed in typical pediatric non-malignant disorders (i.e. immunodeficiencies) rather than in leukemia.

The "molecular man": from the concept of diathesis to HLA associated diseases.

In recent years the concept of biological individuality has found ample acknowledgement in transplantation medicine; yet over 60 years ago Garrod had already grasped its real meaning in terms of a chemical individuality which he in turn envisaged as an explanation for the ancient concept of diathesis. HLA molecules have been recognized as being particularly representative of biological individuality, and their discovery has been followed by the observation that for some diseases there are measurable risks of predisposition which are indeed linked to certain antigenic-molecular HLA conformations. The biological individuality of man is thus acquiring an increasingly well-defined molecular characterization in which ancient diathesis presents a new and effective key for its interpretation.

Elevated IgA anti-gliadin antibodies in juvenile chronic arthritis.

Increased intestinal permeability secondary to treatment with non-steroidal anti-inflammatory drugs (NSAIDs) and raised levels of anti-gliadin antibodies (AGA) have been reported in adults with rheumatoid arthritis. We have therefore retrospectively investigated the presence of serum AGA of the IgA and IgG classes in 70 patients with juvenile chronic arthritis (JCA). Serum IgA (but not IgG) AGA were found to be higher in JCA patients than in controls (6.2 +/- 8.7 vs 2.1 +/- 1.5 AU/ml; p less than 0.0001). This finding was observed independently of the JCA onset subtype or disease activity; however, lower levels of IgA AGA were found in patients with pauciarticular JCA and in those in remission. No significant differences in IgA AGA serum levels were observed between untreated patients and patients treated with NSAIDs. Five patients who presented the highest levels of IgA AGA were further studied a second time; serum IgA AGA were found to be markedly reduced or normalized and no clinical or laboratory evidence of coexistent coeliac disease was observed. In conclusion, our results suggest that the elevation of IgA AGA seen in our patients is secondary to non-specific immune stimulation rather than to an NSAID-induced increase in intestinal permeability.

[The biological Ego. An introspective approach to the natural profile of man]. / L'Io biologico. Un approccio introspettivo al profilo naturale dell'uomo.

To adapt the model of an echosystem to man helps in defining his relationships within the environment in which he lives. To stress the profile of man as "biological Ego" allows a vision in which man is perceived as an organism with unique and unrepeatable immunogical characteristics.

[Leukocytes, between morphology and function]. / Leucociti, fra morfologia e funzione.

Knowledge regarding the immune activity of lymphocytes is quite recent. Polymorphonuclear phagocytosis was described about a century ago, but subdivision of lymphocytes into T and B cells dates back only two decades. Pathophysiologic observations on lymphocytes in the course of infectious mononucleosis have been a source of extremely interesting data. Recognizing different T lymphocyte subsets has enormously enriched knowledge of their functional activities, while the contribution of morphological studies has been very limited.

[Revisiting allergy. 35 years after Ishizaka's discovery of IgE]. / Ripensare le allergie, 35 anni dopo gli Ishizaka.

Some food intolerance ascribable to the individual, namely to the way he reacts to food (in particular, to cheese), was described by Hippocrates (as early as 460-375 B.C.) Since the beginning of modern era, a fascinating literature reports respiratory distress retrospectively viewed as of allergic-asthmatic origin. In the early twenties of 20th century the existence of "reagins" was first signaled, while we have to wait over four decades for the demonstration that these "reagins" were antibodies of the IgE class. However, at the present time, we have reached deep insight into the issue of allergy physio-pathology: from the role of Th2 lymphocytes to that of cytokines selectively involved in the onset of allergic inflammatory reactions, with the future goal of treatments focused more on the physio-pathology of "allergic reactions" than on counteracting its effects.

[The leukemic child after therapy. Psychological aspects]. / Il bambino leucemico in stop-terapia. Aspetti psichici.

Thirty children in remission, at least one year after completing chemotherapy for Acute Lymphoblastic Leukemia, were assessed using general psychological measures. The Wechsler Intelligence tests were administered to evaluate their intellectual function: no significant reduction was found in overall IQ score. Only four of the patients, who presented neurological complications during the treatment, performed at lower levels. The group as a whole functioned poorly on tasks involving speeded performances and long-term memory. The age at diagnosis, the duration of the illness, the cranial irradiation and/or intrathecal-chemotherapy did not show any negative effects on the intellectual performance. Psycho-social adaptation was satisfactory: our patients do not show neurotic or psychotic disorders, but only affective disturbances (insecurity, irritability, poor self-perception, instability and depression). Familial adaptation was disturbed in 60% of the children and difficulty in socializing with peers was present in 57% of cases: the latter, in our experience, is related to poor self perception, present in 75% of our patients. We have found a more inadequate psycho-social adaptation in children who have not received any communication of their illness. Psychologic support can be of value for the child and his family in adapting to their difficult situation and in promoting a normal personality development of the child.

[Diathesis and predisposition. A molecular reappraisal of the mode of reacting]. / Diatesi e predisposizione. Una rivisitazione molecolare del modo di reagire.

The identification of the causes of important infectious and hereditary diseases became scientifically clear in the last years of the nineteenth century and in the first years of the twentieth. Through many centuries, the lack of etiologic knowledge regarding diseases has extraordinarily enhanced the value of the concept of predisposition so that "diathesis" helped to "explain" many forms of morbidity. Several discoveries as to the real "causes" of diseases, however, led to a critical downgrading of its value. But in-depth knowledge regarding the proteins controlled by genes of the "major histocompatibility complex" (MHC, HLA) in man was followed, a few years later, by the demonstration of the fact that carriers of particular alleles are exposed to higher risks of contracting certain diseases than non-carriers of these molecules. A new key for interpretation-this time, a genetic and molecular one-was thus offered for the concept of "predisposition". Actually, man's HLA-associated molecular individuality induces and causes an extraordinarily personal way of reacting to various stimuli. An obvious consequence of this is not only that man, having become aware of his "molecular uniqueness" (which is significantly HLA-related), can view himself as a "biological Ego" but, most of all, that some of his predispositions towards becoming ill may be ascribed to some of his individual molecular characterizations. Thus, the onset and the course of many diseases would be viewed as the effect of a given "way of reacting". This could be recognized as the true essence of diathesis, 18 centuries after Galen.

[Pro-allergy role of infection. A component of the mode of reacting]. / Il ruolo proallergico delle infezioni. Una componente del modo di reagire.

No organism from the cradle lives germ-free or allergen-free. The modalities by which infections facilitate conditions of abnormal reactivity, in particular respiratory asthma and allergy to cow milk proteins, are examined. 216 asthmatic children and 50 infants with rotavirus enteritis have been considered. Infections, besides representing stimuli directly projected on the immune system, also constitute factors which more generally influence the way of reacting.