Sudden infant death syndrome (SIDS): immunoglobulins and hypoxia

Effect of genetic selection for group productivity and longevity on immunological and hematological parameters of chickens

A line of White Leghorn chickens was selected for high group productivity and longevity resulting in improved survival and feather score as well as reduced cannibalism and flightiness. Improvements in survival might have also been due to improved immunity. The present study was designed to test the hypothesis that selection for high (HGPS) and low (LGPS) group productivity and survivability also altered immune and hematological parameters. The LGPS line was an intense reverse selected line of the HGPS line at the eighth generation of development. Hens were randomly assigned to individual cages at 17 wk of age. Blood samples were collected from the hens at 21 wk of age. Subsets of T lymphocytes (CD4+, CD8+, and gammadelta cells) were measured using flow cytometry. Concentrations of plasma IgG were quantified with western blot analysis and immunoprecipitation assay. Hematological parameters were collected from blood smears. The HGPS hens had significantly higher percentages of blood lymphocytes and CD4+:CD8+ ratios of circulating T cells (P < 0.01) and tended to have more, but not significantly, gammadelta T cells (P = 0.07) than the LGPS hens. In contrast, the LGPS hens exhibited eosinophilia and heterophilia and greater heterophil:lymphocyte ratios (P < 0.01). The concentrations of plasma IgG were also significantly higher in the LGPS hens (P < 0.01). These results suggest that genetic selection for group productivity and longevity also alters the immunological and hematological systems of hens. The line difference in regulation of T cells, leukocytes, and production of IgG may suggest that different genes or modes of gene action are involved.

Similarities and differences in lectin cytochemistry of laryngeal and tracheal epithelium and subepithelial seromucous glands in cases of sudden infant death and controls

BACKGROUND

It has been speculated that non-specific defence mechanisms of the epithelium and subepithelial seromucous glands play a role in the larynx and lungs in cases of sudden infant death.

METHODS

The larynx and trachea from five children who had died of sudden infant death (SID) syndrome and five control cases of comparable age were compared for the presence of lectin binding sites (12 different lectins tested).

RESULTS

The secretory product of mucin producing cells contained carbohydrates including galactose and sialic acids. Binding sites for fucose and N-acetyl-galactosamine were only present in some of the specimens and distribution revealed no correlation between cases of SID and controls. Epithelial cells and serous cells of seromucous glands contained binding sites for sialic acid in cases of SID and controls. Moreover, binding sites for mannose were detected in these cells but were only present in SID cases. The difference between the SID and control groups as to the presence/expression of concanavalin A was highly significant.

CONCLUSIONS

It is suggested that mucus hypersecretion in SID occurs in response to bacterial toxins or viral infection and is not specific. The different binding sites for mannose in cases of SID and controls could indicate differences in the production of antimicrobial peptides. A disturbed expression pattern of antimicrobial peptides in children who later succumb to SID could be responsible for an imbalance of the local microflora with a higher density of microorganisms on the mucosa. Further studies are required to elucidate the pattern of expression of antimicrobial peptides in subsequent SID victims.

Intra-alveolar haemorrhage in sudden infant death syndrome: a cause for concern?

BACKGROUND

The "Back to Sleep" campaign in 1991 resulted in a dramatic decrease in the incidence of sudden infant death syndrome (SIDS). The proportion of presumed SIDS deaths being actually suspicious deaths from airway obstruction is likely to have become relatively greater. There is usually little pathological evidence to suggest smothering, but intra-alveolar haemorrhage appears to be more prominent in cases where interference with the airway is suspected.

AIM

To attempt to quantify intra-alveolar haemorrhage to see whether it could be used as a marker to distinguish between smothering/overlaying and SIDS.

METHODS

Intra-alveolar haemorrhage was quantified using digital image analysis on haematoxylin/eosin stained sections taken from the lungs of 62 consecutive infants who had died suddenly and unexpectedly. Cases were initially classified according to the original cause of death. After quantitation, the case histories were critically reviewed. Three pathologists independently made microscopic assessments of the degree of intra-alveolar haemorrhage in the first 24 cases to see whether these accurately reflected the quantitative results.

RESULTS

73% of those infants with a history suggesting possible involuntary overlaying and 45% of those with a history suspicious of smothering had significant intra-alveolar haemorrhage (> 5% of total lung surface area assessed). From the history, the cause of death in 11 cases initially classified as SIDS would better have been given as "Unascertained." Simple microscopic assessments underestimated the true extent of the haemorrhage in 33% (8/24).

CONCLUSIONS

If a moderate degree (at least 5%) of pulmonary parenchymal haemorrhage is observed, this may be an indicator of airway obstruction for a significant period, either from overlaying or possibly smothering. The diagnosis of SIDS may be being used inappropriately in such cases.