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Materno-Fetal Immunity - Introduction (view source)
Revision as of 12:56, 10 August 2010
, 12:56, 10 August 2010Created page with " Passive immunity occurs when 'preformed' antibodies are made in one animal and passed onto another. For example a cow passes on her own antibodies to her calf via colostrum (fir..."
Passive immunity occurs when 'preformed' antibodies are made in one animal and passed onto another. For example a cow passes on her own antibodies to her calf via colostrum (first milk after parturition) and milk.
Antibodies can be transferred to other individuals via colostrum, milk, crossing of the [[Gestation -Placenta - Anatomy & Physiology|placenta]], [[Vaccines - WikiBlood|vaccination]], and plasma transfusions.
Neonates require maternal antibodies because:
'''1. They have poorly developed immune systems and are immunocompromised at birth.'''
'''Lymphocytes in neonates:''' Increased numbers of mostly mature and functional T and B lymphocytes are found in the blood. However the ability to mount an immune response to certain antigens is absent. This may be due to:
# Immaturity of some cells - T helper cells, B cells and Antigen presenting cells.
# Lack of expression of genes encoding receptors for each antigen.
# The presence of maternal antibody which binds antigen and removes it thus preventing the neonate from developing active immunity.
'''Antibodies in neonates:'''
'''2. Neonatal mucosal surfaces are particularly vulnerable'''
'''3. Colostral and milk [[Immunoglobulins|antibodies]] protect neonates from infections'''
==Passive transfer via [[Gestation -Placenta - Anatomy & Physiology|placenta]]==
{| style="width:60%; height:200px" border="1" align=center
!'''SPECIES'''
!'''PLACENTA TYPE'''
!'''IgG TRANSFER?'''
|-
| human
| haemochorial
| YES
|-
| dog/cat
| endotheliochorial
| SMALL AMOUNT
|-
| horse/ruminant/pig
| epitheliochorial
| NO
|-
|}
Due to the placentas of ruminants and horses having 5 tissue layers between the maternal and fetal circulation there is no transfer of [[Immunoglobulins|antibodies]] across the placenta.
==Passive transfer via colostrum==
[[Image:Transfer of IgG across intestine via FcRn.jpg|right|thumb|150px|Transfer of IgG across intestine via FcRn-Brian Catchpole RVC 2008]]
[[Image:PASSIVE TRANSFER.jpg|right|thumb|150px|PASSIVE TRANSFER-M. Maidment RVC 2008]]
[[Image:Colostrum Intake.jpg|right|thumb|150px|Colostrum Intake - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
In the dam [[Lymphoreticular System - Anatomy & Physiology#B cells|B cells]] migrate from the [[Regional Lymphoid Tissue - Anatomy & Physiology|MALT]] to the [[Lactation - The Mammary Gland - Anatomy & Physiology|mammary gland]] where [[Immunoglobulins|antibodies]] are secreted into the colostrum and milk.
===Colostrum===
Colostrum is the pre-milk fluid usually thick and yellow in colour that is secreted from the mammary glands for only a short time after birth by most mammals.
* There is species variation with the composition of colostrum.
*It contains:
** Immune factors - [[Immunoglobulins|immunoglobulins]], lactoferrins, protein-rich polypeptides, leukocytes, cytokines, trypsin and protease inhibitors.
** Growth factors: EgF, IGF-I, IGF-II, FyF, PDGF, TgF A and B and growth hormone (GH) - which aid in rebuilding damaged body systems and stimulating the bodies metabolism to burn fat for energy instead of the bodies own muscle tissue.
** Vitamins and minerals.
*[[Immunoglobulin G|IgG]] is most abudant in colostrum, followed by [[Immunoglobulin A|[[IgA]]]] and [[Immunoglobulin M|IgM]]
* During the first 30 hours of life, [[Immunoglobulins|immunoglobulins]] are absorbed through the intact [[Jejunum - Anatomy & Physiology|jejunum]] and pass to the [[lacteals]], [[Lymphatic Vessels - Anatomy & Physiology|thoracic duct]] and into the systemic circulation.
* The first diagram (entitled Transfer of [[Immunoglobulin G|IgG]] across intestine via FcRn) shows [[Immunoglobulin G|IgG]] being present in the intestine of a neonate, from the ingestion of colostrum. Fc receptors (FcRn) are present on the surface of the intestinal epithelial cell in neonates for the first 30 hours. The [[Immunoglobulin G|IgG]] binds to the receptors and is transported through the cell by pinocytosis and released into the lacteals unchanged.
* The capacity for immunoglobulin absorption progressively declines from birth due to the FcRn only being present for a limited period of time. After 6 hours a third of the FcRn are non functional.
* It is essential that all animals with epitheliochorial placentas (ruminants, horses, pigs) receive adequate colostrum intake within the first 4 hours (optimal absorption period) of life because no transfer of [[Immunoglobulins|immunoglobulins]] via the placenta can occur.
* The second diagram (entitled Passive Transfer) shows the relationship between passive immunity from the mother and the neonatal production of antibodies.
* Colostrum also provides the neonate with a vital energy source to generate heat and enzymes to aid digestion of colostrum products.
==Milk==
Milk is the primary source of nutrition for young before they are able to digest other food.
In non-ruminants [[Immunoglobulin A|'''[[IgA]]''']] is most abundant, followed by [[Immunoglobulin G|IgG]] and [[Immunoglobulin M|IgM]]; [[Immunoglobulin G|'''IgG''']] is most abundant in ruminant milk.
* Milk has approximately 1/100th of the antibody concentration of colostrum.
* Between colostrum and milk there is a period where a substance similar to them both is secreted called transition milk. By approximately 5-7 days milk is being secreted.
* The capacity for [[Immunoglobulins|immunoglobulin]] absorption from the gastrointestinal tract is completely absent 30 hours post partum so the main role of milk (apart from a nutritional source) is to protect the intestinal lining.
* [[IgA]] remain in the intestine and attach to the intestinal villi protecting the intestinal lining against enteric pathogens.
<big><center>'''''Colostrum feeding of lambs and kids'''''</center></big>
{| style="width:60%; height:200px" border="1" align=center
!'''Colostrum source'''
!'''Acceptability'''
|-
| Dam with good quality colostrum
| Best source
|-
| Another female in the flock/frozen colostrum (must be thawed properly)
| Best substitute
|-
| A female in another flock (similar disease status)
| Next best substitute
|-
| Ewe or doe
| There is a risk of transferring diseases for example Maedi Visna and Caprine Arthritis and Encephalitis (CAE) viruses.
|-
| Cow
| Lower in nutrition (milk from coloured breeds is higher in fat), need to feed 1/3 more volume, Johne's risk
|-
| Colostrum supplement powder
| Nutritious, contains antibodies, expensive
|-
| Lamb or kid milk replacer
| Only feed after first 24 hours of life as it is not an adequate substitute for colostrum
|}
[[Category:Materno-Fetal Immunity]]