Guidelines for the use of human immunoglobulin therapy in patients with primary immunodeficiencies in Latin America

Antibodies are an essential component of the adaptative immune response and hold long-term memory of the immunological experiences throughout life. Antibody defects represent approximately half of the well-known primary immunodeficiencies requiring immunoglobulin replacement therapy. In this article, the authors review the current indications and therapeutic protocols in the Latin American environment. Immunoglobulin replacement therapy has been a safe procedure that induces dramatic positive changes in the clinical outcome of patients who carry antibody defects.

Primary immunodeficiency diseases in Latin America: proceedings of the Second Latin American Society for Immunodeficiencies (LASID) Advisory Board

Early diagnosis and appropriate therapy are essential for the best prognosis and quality of life in patients with primary immunodeficiency diseases (PIDDs). Experts from several Latin American countries have been meeting on a regular basis as part of an ongoing effort to improve the diagnosis and treatment of PIDD in this region. Three programmes are in development that will expand education and training and improve access to testing facilities throughout Latin America. These programmes are: an educational outreach programme (The L-Project); an immunology fellowship programme; and the establishment of a laboratory network to expand access to testing facilities. This report provides the status of these programmes based on the most recent discussions and describes the next steps toward full implementation of these programmes.

Serum antibody response to polysaccharides in children with recurrent respiratory tract infections

We evaluated children (15-months old and older) with recurrent upper respiratory tract infections and normal levels of immunoglobulins in serum for specific polysaccharide immunodeficiency using an enzyme-linked immunosorbent assay method. Results showed that of 12 patients vaccinated with Act-HIB vaccine, one did not develop specific antibodies to Haemophilus influenzae type b, demonstrating that such immunodeficiency is present in Costa Rican children.

The mutational spectrum of human malignant autosomal recessive osteopetrosis

Human malignant infantile osteopetrosis (arOP; MIM 259700) is a genetically heterogeneous autosomal recessive disorder of bone metabolism, which, if untreated, has a fatal outcome. Our group, as well as others, have recently identified mutations in the ATP6i (TCIRG1) gene, encoding the a3 subunit of the vacuolar proton pump, which mediates the acidification of the bone/osteoclast interface, are responsible for a subset of this condition. By sequencing the ATP6i gene in arOP patients from 44 unrelated families with a worldwide distribution we have now established that ATP6i mutations are responsible for approximately 50% of patients affected by this disease. The vast majority of these mutations (40 out of 42 alleles, including seven deletions, two insertions, 10 nonsense substitutions and 21 mutations in splice sites) are predicted to cause severe abnormalities in the protein product and are likely to represent null alleles. In addition, we have also analysed nine unrelated arOP patients from Costa Rica, where this disease is apparently much more frequent than elsewhere. All nine Costa Rican patients bore either or both of two missense mutations (G405R and R444L) in amino acid residues which are evolutionarily conserved from yeast to humans. The identification of ATP6i gene mutations in two families allowed us for the first time to perform prenatal diagnosis: both fetuses were predicted not to be affected and two healthy babies were born. This study contributes to the determination of genetic heterogeneity of arOP and allows further delineation of the other genetic defects causing this severe condition.

Membrane and transmembrane signaling in Herpesvirus saimiri-transformed human CD4(+) and CD8(+) T lymphocytes is ATM-independent

In the genetic disorder ataxia telangiectasia (AT), humoral (B) and cellular (T) immunological abnormalities are frequently observed. As a consequence, AT patients are predisposed to life-threatening sinopulmonary infections. The pathogenic mechanisms remain unknown, but a role for ATM in signal transduction from membrane receptors has been proposed. We have explored the effects of a defective ATMgene on isolated human T-lineage cells from 13 AT patients with proven T cell dysfunction by transforming their CD4(+) and CD8(+) T lymphocytes with Herpesvirus saimiri, and analyzing their signaling behavior as compared to normal controls. Several functional parameters were assayed in response to both membrane (anti-CD3 and IL-2) and transmembrane (phorbol myristate acetate plus the calcium ionophore ionomycin) stimuli: (i) calcium mobilization, (ii) induction of activation molecules (CD25, CD40 ligand, CD69 and CD71), (iii) cytokine synthesis (IL-2 and tumor necrosis factor-alpha) and (iv) proliferation. All these early and late activation events were found to be normal in the transformed ATM-/-T cells, indicating that ATM is not necessary for their induction. As expected, ATM-/- transformed T cells showed an increased radiosensitivity by both radioresistant DNA synthesis and cell survival assays. In contrast to an earlier report testing transformed B lymphocytes, our results indicate that transformed mature peripheral T lymphocytes from AT patients do not have intrinsic immune function defects. Rather, the described T-lineage signaling impairments observed in patients may be secondary in vivo to extrinsic ATM-dependent suppressive factors and/or to a developmental defect. These transformed T cells may help to understand the distinct biological role of ATM in different cell types and to develop rational therapies for the immunological dysfunction of AT patients.

Human malignant osteopetrosis: pathophysiology, management and the role of bone marrow transplantation

Osteopetrosis is a heterogeneous group of diseases characterized by lack of osteoclast function. Osteopetrosis is found spontaneously in most mammalian species and many transgenic animals have been created, but so far no animal model has been found that genetically corresponds to human malignant autosomal recessive osteopetrosis. The only curative treatment for malignant osteopetrosis is bone marrow transplantation. A review of the literature and preliminary data from IBMTR shows that infants transplanted with marrow from an HLA-identical sibling or unrelated volunteer donor have an actuarian five-year survival with a functioning graft of 50-70%, while those transplanted with a T-cell-depleted mismatched marrow have a very poor survival of only about 10%.

Visceral leishmaniasis in Costa Rica: first case report

We describe a 15-month-old eutrophic immunocompetent male who presented with fever, hepatosplenomegaly, pancytopenia, and hypergammaglobulinemia. Leishmania amastigotes were identified in spleen and bone marrow specimens. In addition, tissue culture, animal inoculation, and isoenzyme analysis identified the parasite as Leishmania donovani infantum or Leishmania donovani chagasi. The infant was successfully treated with an antimonial drug. These findings represent the first case of visceral leishmaniasis reported in Costa Rica.

Juvenile chronic arthritis in urban San José, Costa Rica: a 2 year prospective study

OBJECTIVE

To find the incidence and prevalence of juvenile chronic arthritis (JCA) in the urban area of San José, Costa Rica.

METHODS

During the year preceding our 2 year prospective, population based study, we conducted an educational program on JCA. The physicians caring for children < 16 years of age from all centers in the study area followed the program. They were asked to refer all cases of possible JCA according to EULAR criteria. The children were all evaluated at the National Children's Hospital.

RESULTS

Of 189 children referred, 48 fulfilled EULAR criteria for JCA. The 2 year incidence rate for JCA was 13.7 per 100,000 children < 16 years old. This corresponds to an annual incidence per 100,000 children of 6.8 (95% CI 4.1-9.6). The incidence rate for pauciarticular onset JCA was 3.9 per 100,000. At the prevalence date, 122 cases of JCA were recorded, corresponding to a prevalence of 34.9 per 100,000 children < 16 years. When patients in remission were excluded, the prevalence was 31.4 per 100,000 (95% CI 25.5-37.2). The pauciarticular onset form was the most common, 71% of all prevalence cases. The highest incidence and prevalence were noted for pauciarticular girls with late onset JCA. No incidence peak was found in preschool age. The girl-to-boy ratio was 1.5/1. Antinuclear antibodies (ANA) were positive in only 7 cases (6.3%). IgM rheumatoid factor was found in 13 children (10.6%). Chronic iritis was observed in 4 cases, all of them ANA negative and older than 7 years of age at onset of arthritis.

CONCLUSION

The incidence and prevalence observed were lower than those reported in other population based studies, but within the confidence intervals of their data. The incidence rate for pauciarticular JCA was significantly lower than that reported in other comparable studies. ANA positive pauciarticular preschool girls and associated uveitis were rarely encountered.

A model for ATM heterozygote identification in a large population: four founder-effect ATM mutations identify most of Costa Rican patients with ataxia telangiectasia

Ataxia telangiectasia (A-T) is an autosomal recessive disorder with a broad range of clinical manifestations and a frequency of 1:40,000-100,000 live births. Epidemiological studies have suggested that A-T heterozygotes are at an elevated risk of breast cancer. ATM mutations occur worldwide over the entire ATM gene, making it difficult to identify heterozygotes in large populations. However, some founder-effect mutations are specific for certain populations. Here, we present four mutations in Costa Rican A-T patients that accounted for 86-93% of 41 patients studied in two batches. We have developed assays for rapid detection of these four mutations which can be used diagnostically. They will also enable the Costa Rican population to be used as a model for analyzing the role of ATM heterozygosity in cancer development and other disorders.

Ataxia-telangiectasia: identification and detection of founder-effect mutations in the ATM gene in ethnic populations

To facilitate the evaluation of ATM heterozygotes for susceptibility to other diseases, such as breast cancer, we have attempted to define the most common mutations and their frequencies in ataxia-telangiectasia (A-T) homozygotes from 10 ethnic populations. Both genomic mutations and their effects on cDNA were characterized. Protein-truncation testing of the entire ATM cDNA detected 92 (66%) truncating mutations in 140 mutant alleles screened. The haplotyping of patients with identical mutations indicates that almost all of these represent common ancestry and that very few spontaneously recurring ATM mutations exist. Assays requiring minimal amounts of genomic DNA were designed to allow rapid screening for common ethnic mutations. These rapid assays detected mutations in 76% of Costa Rican patients (3), 50% of Norwegian patients (1), 25% of Polish patients (4), and 14% of Italian patients (1), as well as in patients of Amish/Mennonite and Irish English backgrounds. Additional mutations were observed in Japanese, Utah Mormon, and African American patients. These assays should facilitate screening for A-T heterozygotes in the populations studied.

Development of a Costa Rican version of the Childhood Health Assessment Questionnaire

OBJECTIVE

To validate a Spanish language version of the Childhood Health Assessment Questionnaire (CHAQ) for use in Costa Rica and to evaluate the feasibility, reliability, and cross cultural equivalency of this version.

METHODS

The original questionnaire, translated without modification into Spanish, was administered to 12 children, all above 10 years of age, with the diagnosis of juvenile chronic arthritis (JCA) and to their parents. There were several problems in comprehension, and self-administration with this version was not possible. For this reason a teacher and a psychologist were consulted to create a modified Costa Rican version. We administered this 2nd version to 46 children with JCA and 62 of their parents.

RESULTS

The modified Costa Rican HAQ (CR-CHAQ) was self-administered by 93.5% of the patients and 84% of the parents. The median time to complete the questionnaire was 12 min for the children, 10 min for the parents. The main difficulty in comprehension was the pain score for both groups. Test-retest (Spearman R = 0.73) and interobserver (Spearman R = 0.70) reliability were good. Validity of the instrument was confirmed by the high correlation between the disability and discomfort scores and conventional clinical variables. There was satisfactory correlation between the disability score and conventional clinical variables. Discriminant validity was confirmed by the capacity of the CR-CHAQ to evaluate patients as being in different categories of disease activity.

CONCLUSION

After modifications, the CR-CHAQ achieved cross cultural equivalency.

Sublocalization of an ataxia-telangiectasia gene distal to D11S384 by ancestral haplotyping in Costa Rican families

In an effort to localize a gene for ataxia-telangiectasia (A-T), we have genotyped 27 affected Costa Rican families, with 13 markers, in the chromosome 11q22-23 region. Significant linkage disequilibrium was detected for 9/13 markers between D11S1816 and D11S1391. Recombination events observed in these pedigrees places A-T between D11S1819 and D11S1960. One ancestral haplotype is common to 24/54 affected chromosomes and roughly two-thirds of the families. Inferred (ancestral) recombination events involving this common haplotype in earlier generations suggest that A-T is distal to D11S384 and proximal to D11S1960. Several other common haplotypes were identified, consistent with multiple mutations in a single gene. When considered together with all other evidence, this study further sublocalizes the major A-T locus to approximately 200 kb, between markers S384 and S535.

Genetic haplotyping of ataxia-telangiectasia families localizes the major gene to an approximately 850 kb region on chromosome 11q23.1

The genotyping data given localize the major A-T gene to an approximately 850 kb region. They also localize the group A A-T gene (ATA) to a region that contains the approximately 850 kb region. They are compatible with linking A-TFresno to 11q22-23. NBS-V2 does not link to this region. Four non-linking families contain only single affecteds, suggesting that these may be spontaneous mutations rather than evidence for an A-T gene outside the 11q22-23 region. Finally, two other non-linking families contain recombinant haplotypes that are compatible with a second A-T gene at 11q22-23, slightly distal to the approximately 850 kb region. However, convincing evidence for a second gene is still lacking.

Juvenile chronic arthritis in Costa Rica. A pilot referral study

In order to adequately care for patients with chronic disorders and to properly allocate resources, the epidemiology of the underlying disease must be know. Proper population based studies involve substantial planning and educational programs, however. To prepare for such a study of pediatric rheumatic disorders, we performed a referral-based pilot study. During an eleven-month period pediatricians all over Costa Rica were asked to refer to us all new cases of possible rheumatic disorders among children less than 16 years of age, using the EULAR criteria for juvenile chronic arthritis. The children were evaluated at the National Children's Hospital. An annual incidence of 5.9 cases of all types of pediatric rheumatic diseases per 100,000 was found. Incidences of 5.4 per 100,000 children below 16 years of age and 6.1 for children below 12 years of age were observed for juvenile chronic arthritis (JCA). 77% of the JCA cases were of pauciarticular onset, and 23% were of polyarticular onset. No cases of systemic JCA were diagnosed. The female to male ratio was 3:2. Antinuclear antibodies were positive in 13% of the JCA cases, and IgM rheumatoid factor was found in 15% of the children. Chronic iritis was noted in only 2 cases; both were girls and both were ANA positive. The incidence found was low compared to population-based studies, but in the same range as hospital-based investigations.

Genetic haplotyping of ataxia-telangiectasia families localizes the major gene to an approximately 850 kb region on chromosome 11q23.1

The genotyping data given localize the major A-T gene to an approximately 850 kb region. They also localize the group A A-T gene (ATA) to a region that contains the approximately 850 kb region. They are compatible with linking A-TFresno to 11q22-23. NBS-V2 does not link to this region. Four non-linking families contain only single affecteds, suggesting that these may be spontaneous mutations rather than evidence for an A-T gene outside the 11q22-23 region. Finally, two other non-linking families contain recombinant haplotypes that are compatible with a second A-T gene at 11q22-23, slightly distal to the approximately 850 kb region. However, convincing evidence for a second gene is still lacking.

Bone marrow transplantation for autosomal recessive osteopetrosis. A report from the Working Party on Inborn Errors of the European Bone Marrow Transplantation Group

The outcomes of 69 patients who received allogeneic bone marrow grafts for autosomal recessive osteopetrosis in the period between 1976 and 1994 were analyzed retrospectively. Four patients received bone marrow transplants (BMT) without prior myeloablative conditioning; transient osteoclast function was demonstrated in one of them. Sixty-five patients received myeloablative pretreatment. Recipients of a genotypically human leukocyte antigen (HLA)-identical BMT had an actuarial probability for 5-year survival, with osteoclast function, of 79%; recipients of a phenotypically HLA-identical bone marrow graft from a related or unrelated donor, or one HLA-mismatched graft from a related donor, had an actuarial probability for 5-year survival, with osteoclast function, of 38%; patients who received a graft from an HLA-haplotype mismatched related donor had a probability for 5-year survival of only 13%. The main problems in haplotype-nonidentical BMT were graft failure and BMT-related complications such as sepsis, bleeding, and interstitial pneumonia. Osteoclast function developed in all patients with full engraftment. Recovery of osteoclast function was associated with severe hypercalcemia in 24% of the patients with engraftment, especially those older than 2 years of age. At the time of BMT, severe visual impairment was present in 35% of the patients; of the 15 patients who had visual impairment at the time that a successful BMT was performed, two had improvement after BMT (13%). Within the total group, one patient had neurodegeneration. Engraftment of healthy donor cells had no influence on the progression of that abnormality and BMT thus had no beneficial effect on this phenotype of osteopetrosis. In general, however, early BMT remains the only curative treatment for autosomal recessive osteopetrosis.

Lack of correlation of in vitro adherence of Haemophilus influenzae to epithelial cells with frequent occurrence of otitis media

The adherence to human epithelial cells, biotype and capsular type of 175 Haemophilus influenzae cultured from the upper respiratory tract were studied in a prospective study of children with recurrent otitis media. Forty-three children who had greater than 2 episodes of acute otitis media (AOM) during the first year of life were followed for at least 1 year. Cultures of the oropharynx were done periodically, and the middle ear fluid (MEF) was cultured at the time of AOM. H. influenzae was recovered from MEF in 44% of the 136 AOM episodes recorded. Thirty-one children had at least one episode of AOM caused by H. influenzae; the remaining 12 children, designated as "controls," had no otitis or had AOM caused by other organisms. The possible differences between carriage and infection strains were evaluated by comparison of MEF and oropharyngeal isolates, by pairwise comparison of MEF and oropharyngeal isolates and by pairwise comparison of multiple isolates from each host recovered at the time of AOM and during infection-free intervals. No significant differences in patterns of adherence, capsular type or biotype were found. The lack of correlation between these characteristics and infection suggests either that H. influenzae organisms have determinants of virulence yet to be defined or that variations in host susceptibility permit infection by the strain colonizing the upper respiratory tract. Adherence per se may be less important in the development of infection than in establishing and maintaining colonization within the host.

Application of multilocus enzyme gel electrophoresis to Haemophilus influenzae

Multilocus enzyme electrophoresis was adapted to the study of Haemophilus influenzae. Protein extracts from sonicated whole bacteria were subjected to starch gel electrophoresis. After staining with substrates, the position of each isoenzyme (electromorph) was registered. Each isolate was assigned an electrophoretic type (ET) by the combination of electromorphs for the enzymes stained. Twenty-seven enzymes were tested; 12 were expressed in H. influenzae. Six enzymes were selected for subsequent study: malate dehydrogenase (MDH), phenylalanylleucine peptidase (PE2), 6-phosphogluconate dehydrogenase (6PG), adenylate kinase (AK), glucose 6-phosphate dehydrogenase (G6P), and phosphoglucose isomerase (PGI). They were polymorphic and occurred in all isolates. Six electromorphs were found for PE2, G6P, and PGI, five for MDH, four for 6PG, and three for AK. PE2, G6P, and PGI contributed most of the ET resolution (48 of 49 ETs). Multilocus enzyme electrophoresis showed several advantages over previous typing techniques. An ET could be assigned to both typable and nontypable (NT) isolates. The technique was powerful in resolving differences among isolates. The 94 isolates comprised 49 ETs, five biotypes, and six capsular types and NT isolates. Strains known to be related expressed the same ET, e.g., RAB b+ and b-, ET12; Ma a+ and a-, ET1. ET variability among type b isolates was low; 26 of 28 clinical isolates expressed ET14; 2 of 28 expressed ET13 and ET15, differing from ET14 by one electromorph each. In contrast, the 47 NT isolates comprised 38 different ETs. No ETs were shared between non-type b capsulated strains and type b or NT strains. Interestingly, five NT isolates expressed the same ET as type b strains. (iv) Strains of the same capsular type but different biotypes expressed different ETs. ET determinations will thus be useful in studying the epidemiology and evolution of H. influenzae.

Difference in structure between type b and nontypable Haemophilus influenzae populations

The extent of chromosomal genetic variability and the genetic structure of Haemophilus influenzae populations was analyzed. A total of 119 isolates from humans in Göteborg, Sweden, and Birmingham, Ala., and 16 strains from a type culture collection were characterized for capsular type, biotype, outer membrane protein profile, and enzyme electrophoretic type (ET). The results of this study indicate that the bacteria identified as H. influenzae are a genetically extremely variable array of organisms. For the six enzymes studied, the estimated mean genetic diversity was 0.57 (approximately 20% higher than the corresponding estimate for Escherichia coli). Two lines of evidence indicate that despite its ability to recombine by transformation, H. influenzae maintains a largely clonal population structure. Although there is considerable potential for generating different genotypes, there were only 88 distinct ETs among the 135 strains, and isolates of the same ET and biotype were recovered at frequencies greater than would be anticipated at random. This evidence for a clonal population structure holds for uncapsulated as well as capsulated strains. However, these data also suggest that the stability of H. influenzae clones (clone persistence time) may be less than that of the nontransforming species E. coli. The ET data indicate that there is somewhat less variability among H. influenzae strains that express the same capsular antigens, biotype, and outer membrane proteins than among randomly chosen isolates. Nevertheless, there is substantial genetic variation among isolates within each of these classes and combinations thereof. There is also variation in these typing characteristics among strains of the same ET. These observations and those on genetic variability and population structures have implications for the characterization of H. influenzae isolates in clinical and epidemiological studies.

Inhibition of attachment of Streptococcus pneumoniae and Haemophilus influenzae by human milk and receptor oligosaccharides

Human milk inhibited the attachment of Streptococcus pneumoniae and Haemophilus influenzae to human pharyngeal or buccal epithelial cells. Infant formulas and cow and buffalo milk showed a lower inhibitory activity against pneumococci and enhanced the adhesion of H. influenzae. The antiadhesive effect against S. pneumoniae was found in both the high- and the low-molecular-weight fractions of milk. The inhibitory activity in the high-molecular-weight fraction was independent of specific antibody content; it was present after immunoadsorption and in the milk from IgA-deficient women. The inhibitory activity in the low-molecular-weight fraction was in part explained by the content of oligosaccharides corresponding to the carbohydrate moieties of the neolactoseries of glycolipids, which have previously been shown to act as receptors for attaching pneumococci. The antiadhesive activity against H. influenzae was restricted to the high-molecular-weight fraction of the milk and was unaffected by immunoadsorption. Milk may protect against otitis by reducing colonization.

The secretory IgA system

The secretory IgA system is common to all mucosal membranes and is presumably of great importance for their defense. In addition to the secretory IgA antibodies produced in a mucosa in response to a local antigenic stimulus there is a spread of this type of IgA response via committed lymphocytes. They originate from central lymphoid organs in the intestinal (Peyer's patches) and bronchial mucosa (bronchus-associated lymphoid tissue, BALT) which they leave after antigenic exposure. They migrate, or "home", to exocrine glands such as the lacrimal, salivary, mammary and prostatic glands and mucosal membranes of the respiratory, gastrointestinal and genito-urinary tract. Almost half of all lymphocytes may be involved in the production of IgA antibodies. The secretory IgA antibodies are the dominating immunoglobulins in exocrine secretions on mucous membranes. They function primarily by preventing contact between the microbe and the host tissue most commonly attacked in infections, the mucous membrane. The fact that breast-feeding protects the infant against intestinal infections is one good example of the clinical significance of secretory IgA antibodies. This mode of protection can be enhanced by vaccination.

Method for testing adherence of Haemophilus influenzae to human buccal epithelial cells

A method for testing adherence of Haemophilus influenzae strains to buccal mucosal cells is described. Bacteria grown in broth for 4 h were mixed with buccal mucosal cells. After elimination of unattached bacteria by repeated cycles of centrifugation and resuspension in PBS, the number of attached bacteria was counted microscopically. Optimal results were obtained with an early log-phase bacterial culture at a concentration of 10(9) bacteria/ml mixed with 2 X 10(4) cells/ml and incubated at 37 degrees C for 60 min. This assay showed an at least ten times higher rate of adherence for Haemophilus influenzae than previous studies. Nontypeable strains attached in higher numbers than strains with the type b capsule. Adherence was related to the frequency of nontypeable strains rather than to the site of isolation or type of infection. Thus all the isolates from middle ear fluid were nontypeable, and all but one adhered. The results suggest a difference in virulence mechanisms between type b and nontypeable Haemophilus influenzae strains.

Defence of mucous membranes by antibodies, receptor analogues and non-specific host factors

Most infections reach man via the mucosal membranes, and more than half of the lymphoid system is found in connection with mucosae. The major antibodies found on mucous membranes are secretory IgA, which function primarily by binding microorganisms and thereby preventing their contact with the host tissues. The optimal mode of immunization to obtain a secretory IgA response is not well defined. Repeated mucosal exposure with antigen may result in oral tolerance, with decreasing circulating antibodies but a remaining secretory IgA response. The secretory IgA response is usually short-lived and can be difficult to boost. IgM as well as IgG antibodies may add to host defence at the mucosal level, but when engaged, they usually induce inflammation in host tissues. Analogues to bacterial receptors on mucosal epithelium may be present in exocrine secretions such as human milk. During an attack on the host, it is possible that such receptor analogues may aid in the prevention of attachment of bacteria to mucous membranes used as an initial site. A number of non-specific host factors support mucosal defence. One of them is lactoferrin. Lactoferrin deficiency seems to result in recurrent bacterial infections, suggesting its importance in normal host defence.

Protective factors in milk and the development of the immune system

The neonate is immature in certain immunologic functions. The slow development of secretory immunoglobin A (IgA) seems to be compensated by selective transfer of secretory IgM into exocrine secretions on mucous membranes during the first few months of life. Secretory IgA and secretory IgM antibodies against Escherichia coli and poliovirus are already found in the neonate, possibly in response to the maternal anti-idiotypic IgG antibodies transplacentally exposing the fetus. Via such a mechanism, food antibodies could occur before direct food exposure in the infant. Human milk provides large amounts of antibodies (as a crude comparison, about 50 times the amount of antibodies given to a patient with hypogammaglobulinemia). The milk antibodies, dominated by secretory IgA, protect especially against intestinal infections. The milk also contains oligosaccharide analogues to epithelial receptors for bacteria. They, as well as a number of milk components such as lactoferrin and lysozyme, may contribute to host defense. The food antibodies in human milk may influence the infant's immune response to foreign food proteins introduced during weaning.

Detection of soy protein in soy lecithin, margarine and, occasionally, soy oil

Samples of soy lecithin, soy oil and margarine were tested for the presence of soy proteins by an inhibition technique using ELISA. All but one of the soy lecithin samples contained soy protein, as did some of the soy oil and margarine samples. The positive margarines contained only about 25% as much soy protein as the soy lecithin preparations. The presence of soy proteins in these soy products might account for hitherto unrecognized exposure to soy proteins in various foods.

The immune response of the mammary gland and its significance for the neonate

The immune response of the mammary gland is dominated by local production of secretory IgA antibodies (SIgA). These milk antibodies, amounting to about 0.5-1 g/day throughout lactation, are directed against food proteins and microorganisms often present in the intestine. This is presumably explained by the enteromammaric link: after antigenic exposure in the Peyer's patches of lymphoid cells they home to various exocrine glands, including the mammary gland. Similarly, lymphoid cells from the bronchial mucosa, may contribute to the antibody-producing cell population in the mammary gland. SIgA antibodies against common foods like cow's milk and soy proteins are regularly found in milk if such proteins are part of the mother's diet. It is possible, but unproven, that milk antibodies can decrease the exposure of the infant's intestinal mucosa to foreign food proteins introduced during continued breast-feeding. Milk SIgA antibodies do not prevent intestinal colonization by microorganisms, against which the milk antibodies are directed. The SIgA antibodies are thought to exert protection primarily by preventing contact between the microorganisms and the mucosal membranes. In this manner, human milk blocks attachment of otitis media-causing strains of pneumococci and H. influenzae to retropharyngeal cells, possibly explaining why breast-feeding may prevent otitis media. Milk antibodies have anti-attachment capacity, but there is also low molecular weight material in the milk with this capacity. It probably consists of analogues to the oligosaccharide receptor for pneumococci on the retropharyngeal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Defence of mucous membranes by antibodies, receptor analogues and non-specific host factors

Most infections reach man via the mucosal membranes, and more than half of the lymphoid system is found in connection with mucosae. The major antibodies found on mucous membranes are secretory IgA, which function primarily by binding microorganisms and thereby preventing their contact with the host tissues. The optimal mode of immunization to obtain a secretory IgA response is not well defined. Repeated mucosal exposure with antigen may result in oral tolerance, with decreasing circulating antibodies but a remaining secretory IgA response. The secretory IgA response is usually short-lived and can be difficult to boost. IgM as well as IgG antibodies may add to host defence at the mucosal level, but when engaged, they usually induce inflammation in host tissues. Analogues to bacterial receptors on mucosal epithelium may be present in exocrine secretions such as human milk. During an attack on the host, it is possible that such receptor analogues may aid in the prevention of attachment of bacteria to mucous membranes used as an initial site. A number of non-specific host factors support mucosal defence. One of them is lactoferrin. Lactoferrin deficiency seems to result in recurrent bacterial infections, suggesting its importance in normal host defence.

Food and immunological development

The infant's host defence is deficient in IgA for mucosal protection and also in IgG2 for protection against encapsulated bacteria. The baby is provided with about one gram a day of milk secretory IgA antibodies against most intestinal microorganisms and also food proteins. These milk antibodies together with a number of other defence factors in the milk protect the baby against gastrointestinal and respiratory infections. Maternal undernutrition does not necessarily diminish the milk IgA concentration or 24 hour output. The infant seems to be low in secretory IgA antibodies for several months as studied in saliva. It is of great importance to protect mucosal membranes especially the intestinal mucosa, so that its nutrient uptake is not disturbed. Infections in infancy especially in the gastrointestinal tract is an important cause of undernutrition. The human milk antibodies against cow's milk and soy protein may decrease the exposure to these food proteins during weaning and possibly decrease the risk of developing allergy. Soy oil can contain soy protein, which may explain some food intolerance reactions.