Le. Logdberg et al., Tissue distribution of the lipocalin alpha-1 microglobulin in the developing human fetus, J HIST CYTO, 48(11), 2000, pp. 1545-1552
Alpha-1 microglobulin (alpha (1)m), a lipocalin, is an evolutionarily conse
rved immunomodulatory plasma protein. in all species studied, arm is synthe
sized by hepatocytes and catabolized in the renal proximal tubular cells. a
lpha (1)m deficiency has not been reported in any species, suggesting that
its absence is lethal and indicating an important physiological role for th
is protein To clarify its functional role, tissue distribution studies are
crucial. Such studies in humans have been restricted largely to adult fresh
/frozen tissue. Formalin-fixed. paraffin-embedded multi-organ block tissue
from aborted fetuses (gestational age range 7-22 weeks) was immunohistochem
ically examined for alpha (1)m reactivity. Moderate to strong reactivity wa
s seen at all ages in hepatocytes, renal proximal tubule cells, and a subse
t of pancreatic islet cells. Muscle (cardiac, skeletal, or smooth), adrenal
cortex, a scattered subset of intestinal mucosal cells, tips of small inte
stinal villi, and Leydig cells showed weaker and/or variable levels of reac
tivity. Connective tissue stained with variable location and intensity. The
following cells/sites were consistently negative: thymus, spleen, hematopo
ietic cells, lung parenchyma, glomeruli, exocrine pancreas, epidermis, cart
ilage/bone, ovary, seminiferous tubules, epididymis, thyroid, and parathyro
id. The results underscore the dominant role of liver and kidney in fetal a
lpha (1)m metabolism and provide a framework for understanding the function
al role of this immunoregulatory protein.