Immunity in the Fetus and Newborn
Introduction 
When a mammal is born, emerging from the sterile uterus to an environment in which they are immediately exposed to a large number of microorganisms. To survive, the neonate must be capable of controlling microbial invasion in no time. In practice, the immune system is unable to have a fast start by itself. In animals with short gestation period of the immune system is fully developed and in animals with long gestation period is not expected that the immune system is equal to that of adults.
full development immune activity depends on the antigenic stimulus.
The formation of antigen-sensitive cells depends on the proliferation induced by these antigens. Thus mammals and birds are very sensitive in the first weeks of life.
passive transfer from mother to infant in the form of antibodies and T cells maybe essential for survival.
Objectives To know the immune system development in fetal life of mammals. • Identify
neonatal immune responses.
To know the development of passive immunity and vaccination practices in the newborn.
Fetus and Immunity Newborn
The ontogenesis of immune organs runs in different animal species and humans is very similar, although at the time of birth is found in varying degrees of development.
The thymus is the first lymphoid organ to form, followed by secondary lymphoid organs, the bursa are developed in all mammals and birds at the time of birth, while the establishment and development of other lymphoid organs can recognize the ostensible differences.
inmunuglubulinas containing cells develop soon after the appearance of the spleen and lymph nodes, but antibodies almost never found until the end of fetal life, if they occur before birth.
fetal ability to respond to antigen develops very rapidly after appearing lymphoid organs, but not all antigens have the same ability to stimulate fetal lymphoid tissue. This is handled by the possibility to react to most foreign antigens obtained in a very short time.
The ability to establish cell-type immune responses develops at the same time that the production of antibodies.
The cause of the formation and reactivity of the immune system of newborns is different from one to another species and different brands, is less a result of a disproportionate maturation of this organ system, that the fact that the birth takes place at various stages of ontogeny.
immune response capacity is developed parallel to the formation of the bodies responsible for the immune response. Fetal organs, and partly newborn body can not react to an action still antigenic immune to the same extent in the adult individual. In the field of cellular immune response, the maturation process that the xeno immune - and allogeneic, which el organismo adulto rechaza regularmente en el plazo característico para la relación donante receptor, en fases precoces del desarrollo pre – o postnatal son rechazados con demora o incluso tolerados en virtud de estar la capacidad inmunológica todavía sin constituir por completo.
Becerro
El sistema inmunitario del becerro se forma al principio de la vida fetal. Aunque en el periodo de gestación de la vaca es de 280 días, el timo ya puede reconocerse a los cuarenta días de la concepción. La medula ósea y el bazo aparecen a los 55 días.
Los ganglios linfáticos pueden observarse a los 60 días. Pero las placas de Peyer no aparecen hasta los 175 días.
Los linfocitos peripheral blood are identified in bovine fetuses 45 days, B cells INM + day 59 and day producing InC 135. The time of appearance of serum antibodies depends on the sensitivity of the techniques used. It is therefore not accidental that detectable immune responses are those directed at virus, and therefore highly sensitive tests are required for virus neutralization.
There are reports that calves respond to rotavirus at 73 days, 93 day parvoviruus and parainfluenza virus 3 to 120 days. Of bovine blood lymphocytes may respond to fitohemaglutinacion, the mitogen concanavalin A and of pokeweed between 75 and 80 days, but this capacity is temporarily lost to the moment of birth, due to high serum concentrations of steroids. Piglet
The gestation period of the sow is 115 days on average. The thymus develops 40 days after conception, fetuses can parvoviruus PRODIC antibodies at 58 days and reject allografts since. Blood lymphocytes can respond to mitogens between 48 and 54 days after conception.
The activity of natural killer cells (NK) does not develop until weeks after birth vain. The number of cells Circulating B rises too high after 71 and 80 days. The fetal response to mainly IgM, but fetal and neonatal piglets also produce a small immunoglobulin light chains can have. Colt
The mare's gestation period is approximately 340 days. Lymphoid cells were first observed in the thymus, 60 and 80 days after conception. Found in lymph nodes in the mesentery and intestinal lamina propria at 90 days, and spleen at 175 days. Blood lymphocytes appear towards the 80 days, you may see a few plasma cells from 240 days. Newborn foals infants have detectable quantities of serum IgM and IgG and occasionally IgG (T). Carnivores
The gestation period is 60 days. The volume is detectable at 23 - 33 days. Lymph nodes were identified within 45 days of gestation and in the spleen at 50 - 55 days of pregnancy at this stage puppies can become resistant to an intrauterine injection of antigen by day 42. Chickens
primordial cells arise in the yolk sac membrane and flow through Chemotactic influx into the thymus and bursa of Fabricius from 7 to 5 days of incubation.
lymphocytes with surface IgM can be detected in the bag after forty 14 and antibodies against hemocyanin Bocabella stage and sheep red blood cells can at 16 and 18 days.
lymphocytes with surface IgG will be held on 21 around the time of hatching, while positive cells compared to IgA in the intestine appear three to seven days after hatching.
phagocytic capacity development
By the time of birth, decreases phagocytosis and bactericidal capacity of leukocytes, and increased fetal glucocorticoid concentration. After birth is depressed chemotactic response of macrophages and are able to maintain growth of some viruses, unlike of macrophages from adult specimens. Virucidal activity is acquired gradually, but, apparently, this process is roll the influence of the thymus.
interesting changes occur in the distribution of macrophages in the newborn pig. For example, these pigs have few pulmonary intravascular macrophages. However, during the first days after birth, blood monocytes acquire the pulmonary capillary endothelium and differentiate into macrophages. So in the newborn piglet most particles (75%) were removed from the blood in the liver and spleen. By two months of age, 75% is eliminated in the lungs. Alveolar macrophages from pigs neonates have poor phagocytic activity, but for the 7 days old, is already effective.
Immune System Development and Intrauterine Infection
Although the fetus is not completely helpless, is less able to fight infection as adults. It has been shown that tissues of calves 95 days of gestation produce alpha and beta interferons in amounts similar to those generated in adult tissues. However, it is known that the fetus produces less interferon gamma.
Consequently there are several diseases that can be mild and undetectable in the mother and severe or lethal to the fetus. Examples of these diseases is bluetongue, infectious bovine rhinotracheitis, diarrhea Bovine virus, rubella in humans and taxoplasmosis. Fatal infections often cause lymphoid hyperplasia and increased concentration of immunoglobulins. For that reason, the presence of significant concentrations of immunoglobulins in a newborn animal which has not received breast milk, is indicative of intrauterine antigenic stimulation.
In general the response to these organisms is determined in the state of fetal immune development. For example, if the vaccine for bluetongue virus which is not pathogenic to normal adult sheep applies to gestatantes sheep at 50 days of conception, causes serious injury to the nervous system of the fetus, including hydrocephalus and retinal dysplasia. And if this vaccine is 100 days after conception to newborn lambs were only observed glial response. If the vaccine virus Bluetongue is applied in fetal sheep between 50 and 70 days, this development can be isolated from tissues of the lamb for several weeks, but if you apply after 100 days, almost never be isolated again.
Immune Response in Infants After developing in the sterile environment of the womb, newborn mammals come to an environment rich in microorganisms. The children of pets can provide immune responses at birth. However, any immune response in a newborn animal must be the primary type, with a long delay and low concentrations of antibodies.
therefore provide assistance unless utero, a newborn animal must be the primary type, with a long delay and low concentrations of antibodies.
Therefore, unless assistance is provided in utero, newborn animals may die from infections that pose a lesser threat to the adult. This aid is given immunity in the form of antibody that the mother passes to her children Atraves colostrum. Maternal lymphocytes can also be transferred to the fetus through the placenta to the two infants in the colostrum transintestinal and migration, although the biological significance is unclear.
transfer immunity from mother to Breeding
The route by which maternal antibodies to the fetus is determined by placental structure. In humans and other primates, the placenta is hemocorionica, ie the mother's blood establishes direct contact with the trophoblast. This type of placenta allows maternal IgG is transferred to the fetus, but not the IgM, IgA or IgE. maternal IgG enters the bloodstream of the fetus and the newborn human can have this immunoglobulin concentrations comparable to those of the immunoglobulins concentrations comparable to those of his mother.
Dogs and Cats endoteliocorionica have a placenta in which the chorionic epithelium in contact with the endothelium of maternal caoilares. In these species, a small amount of IgG can pass from mother to puppy or kitten, but most is obtained from the colostrum.
The sidesmocorionica placenta of ruminants, ie, the chorionic epithelium is in direct contact with the uterine tissues, while the placenta of horses and pigs are epiteliocorionicas, as the fetal chorionic epithelium contacts the uterine epithelium intact. In animals with these types of placenta may not be the transplacental passage of molecules of immunoglobulins, and infants and of these species are entirely dependent on the antibodies that are through the colostrum. Passive Immunity
Importance of Maternal Antibodies to Newborn
Under exposure to which is subjected in the course of postnatal development compared with environmental antigens, the organism enters in place of antibodies and specifically sensitized lymphocytes against most of the organism from its environment. If the organism acquires in this way a sufficiently large repertoire of antibodies, would also have against incoming pathogenic antibodies and lymphocytes that can with some determinants of the germ in question, along with the protection specified in the strict sense, the system therefore can be trained immune also confer some immunity nonspecific cross-reaction.
The newborn has only minimal amounts of antibodies AutoShapes, due to the obvious lack of exposure to antigens in prenatal life and as a result of more oi less marked immunological immaturity. even if the newborn was in a position to react with the same intensity that the animal
more by the many microorganisms that work after childbirth, a long time to elapse to have antibodies.
Secretion and Composition of Colostrum and Milk Colostrum represents
secretions accumulated in the mammary gland during the last weeks of pregnancy, along with proteins that are actively transferred from the blood stream under the influence of estrogen and progesterone. Therefore, it is rich in IgG and IgA, but also contains some IgM and IgE. The predominant immunoglobulin in colostrum of most domestic mammals is IgG, which represents up to 65 to 90% of total antibodies. The immunoglobulin IgA and other components are almost always smaller, but important.
As lactation progresses and becomes colostrum milk, there are differences between species. Colostrum absorption
Young animals received breast milk shortly after birth, colostrum lead to digestive tract.
Consequently, calves fed naturally eat an average of two liters of colostrum, although some calves in particular can even drink 6 liters. In these animals the degree of proteolytic activity in the digestive tract is low and is reduced to a more for the trypsin inhibitors of colostrum do not degrade, nor used as a food source, however reaches the intestine intact infants this receptor is a heterodimer of MHC class 1b containing a large alpha chain and microglubulinas b 2. is possible that the FcRn is found in all mammals, and is very similar to Fc receptor found in the yolk sac of chickens. Once
that bind to FcRn, epithelial cells actively capture immunoglobulins through pinocytosis and through these cells into the quiloferos absorbed reaches the systemic circulation and infants vy has a massive transfusion of maternal immunoglobulin. Lack
Passive Transfer
The initial absorption of IgG from the colostrum is necessary for the protection of the young animal against a septicaemic disease.
continuous intake is important IgA or IgG1 against enteric diseases. And the failure of any of these processes predisposes the animal to infection. There are three reasons
leading to the lack of adequate transfer of colostrum. First to the mother to produce in sufficient quantity or of poor quality in cases of premature birth. Secondly even if colostrum is produced in large quantities sufientes the infant may not eat enough (failure of intake). Thirdly, it is possible a defect in intestinal absorption despite an adequate intake of colostrum (failure of absorption).
Development of the Immune Response in Infants
local immune reaction time the colostrum milk becomes, the lymphoid tissues of intestine of neonatal and acquired a total capacity of response to ingested antigens. Much This early response is attributed to interferon but there is an answer early intestinal IgM switching to IgA two weeks later. In the anime the growing response and continue to appear before the numbers of adults reached much earlier than other Igs. This ability of the intestine virgin vouch promptly antigens
systemic immune reaction
The intensity of immune response is regulated in part by a negative feedback that the specific antibody binding FCRS blocks B cell antigen receptor activity of B cells which inhibits most production of antibodies with the same specificity. Passive immunization newborn, maternal antibodies inhibit the development of the young animal's immune action, probably due to the elimination of B cells and antigen enmascaramiewnto and kidnapping. Colostrum may also contain immunosuppressive than immunoglobulins.
Vaccination in Young Animal
Pets newborns are able to develop a sharp response and in the first days of life.
With the choice of appropriate aids and implementing appropriate dose of antigen, it should be possible, at least at the corners, used also in newborns all vaccines used in the adult animal to induce immune responses, although weaker in the quantitative aspect. Because
especially attributed the relative weakness of the immune response capacity to the primary reaction, loses practical significance in repeated shots. The vaccination of newborns is the beginning and should therefore be used as a measure epizotiológica to fight against infectious diseases.
newborn vaccination is limited by the level of maturity of the immune system by the suppressive action of the unit of maternal antibodies may be present.
Despite the ability of young animals react inmunologicamanete a actively acquired protection vaccination carried out even on the first day of life is not usually set before the two weeks of existence. Therefore a
immunoprophylaxis of infectious diseases that occur in the first two weeks of lonely existence can be achieved by vaccination of the mother and subsequent passive contribution to the newborn of maternal antibodies or by direct contribution of immune serum. Conclusions
• The ontogeny of immune organs runs in different animal species and humans is very similar, although at the time of birth is found in varying degrees of development.
• Although the fetus is not completely helpless is less able to fight infection as adults.
· The children of pets can provide immune responses at birth. However, any immune response in a newborn animal must be the primary type, with a long delay and low concentrations of antibodies.
• The continuous intake of IgA and IgG1 is important against enteric diseases. And the failure of any of these processes predisposes the animal to infection. Bibliography
· Friedhelm HORSCH, Immunoprophylaxis of Domestic Animals. Editorial Acribia Spain 1986.
· IAN. R. Tizard, Veterinary Immunology, Fifth Edition, publisher, McGraw-Hill. College Station Texas 1996.
· HALLIDAY. R. Immunity and health in newborns. Jl AJM Editorial Vet. 1985
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