Sudden infant death syndrome Part 2: the response of the reticuloendothelial system to hypoxemia and infection

Cytokines and sudden infant death

BACKGROUND

It has been hypothesised that inflammatory reactions could play an important role in the pathway(s) leading to sudden and unexpected death in infancy. On a molecular level, these reactions are regulated by various cytokines.

METHODS

To characterise the role of IL-1ß, IL-6 and TNFα more precisely, the concentrations of these cytokines were determined quantitatively using specific ELISA techniques in serum and cerebrospinal fluid (CSF) in 119 cases of sudden infant death. The infants were grouped into four categories (SIDS, SIDS with infection, natural death due to infection and unnatural death).

RESULTS

A good correlation was found between CSF and serum for IL-6 (Spearman correlation coefficients (SCC), 0.73) and also for TNFα (SCC, 0.57), although the CSF concentrations were lower than that from the serum. There were no significant differences between the categories of death for any of the serum or CSF cytokines. Compared with normal values, increased serum concentrations of IL-1ß, IL-6 and TNFα were found in 70%, 69% and 38% of the cases respectively, indicating possible agonal or post-mortem changes of cytokine concentrations. In three cases very high cytokine concentrations were found (mainly for IL-6). This may have contributed to the mechanism of death (cytokine storm) in two of the cases.

CONCLUSIONS

In a small group of patients, very high cytokine concentrations are a possible explanation for the cause of death ("cytokine storm").

Extramedullary haematopoiesis in liver of sudden infant death cases

AIMS

To determine the frequency of extramedullary haematopoiesis (EMH) in sudden infant death and control cases, and to provide descriptive data on extramedullary haematopoietic islands and diffuse cells.

METHODS

The study was carried out in 51 SIDS and 102 non-SIDS cases. Liver-tissue sections were stained with haematoxylin and eosin, and immunohistochemistry was done with streptavidin-biotin-peroxidase complexes by Polyclonal Haemoglobin "A" antibody. The prevalence of data was estimated statistically by Pearson chi-square test, descriptive statistics, and Kruskal-Wallis test.

RESULTS

The Pearson chi-square values (CI: 95%; OR: 0.071-0.49; p: 0.0474) show higher frequency of EMH islands in SIDS than in controls. The number of diffuse extramedullary haematopoetic cells was higher in SIDS cases compared to non-SIDS (p=0.017).

CONCLUSIONS

EMH is a frequent finding in SIDS cases, and this may be a consequence of anaemia associated with intrauterine hypoxia, or infections.

Sudden infant death syndrome and enteric infection

The association of Helicobacter pylori in the stomach, trachea and lungs with the incidence of SIDS, gastric ulcers and cancer may have a counterpart in animals. In field studies of white muscle disease (WMD) and hepatic necrosis in selenium-deficient pigs dying suddenly, veterinarians identified gastric ulcers in 40% of inspected piglets. The lesion was also commonly observed by researchers in experimentally produced vitamin E-selenium deficiency and other researchers suspected that gastric ulcers in swine may be associated with vitamin E-selenium deficiency. Mice preferentially concentrated (75)selenium in peritoneal exudative cells (PEC) when (75)selenium as selenium selenate was administered by stomach tube to selenium-deficient mice. Selenium concentrated in PECs as glutathione peroxidase (GSHP(x)). GSHP(x)-deficient leucocytes in peritoneal exudate failed to kill yeast cells. GSHP(x) deficiency has also been associated with decreased microbicidal activity of leucocytes in patients with chronic granulomatosis. The selenium-deficient swine were usually growing rapidly in crowded conditions, and, apart from WMD and hepatic necrosis, edema was prominent in the spiral colon, subcutaneous tissues, lungs and submucosa of the stomach. The elevated immunological response in the spleen and lungs of SIDS victims suggests an initial defective microbicidal propensity of the peritoneal exudative cells.