Alpha2 macroglobulin elevation without an acute phase response in depressed adults with Down's syndrome: implications.
Alpha2 macroglobulin may signal depression in adults with Down syndrome even when common inflammation markers look normal.
01Research in Context
What this study did
The team drew blood from adults with Down syndrome. Some had depression. Some did not.
They checked alpha2 macroglobulin, a big blood protein. They also checked classic inflammation markers like CRP.
Goal: see if depression in Down syndrome shows the same inflammation spike seen in other groups.
What they found
Depressed adults with Down syndrome had higher alpha2 macroglobulin.
Surprise: the usual inflammation markers stayed flat.
This hints that alpha2 macroglobulin could flag depression in this group even when classic inflammation is missing.
How this fits with other research
English et al. (1995) first mapped how depression looks in adults with Down syndrome—lots of quiet withdrawal and visual hallucinations. The new blood data now give a possible biological red flag for those same patients.
Mulder et al. (2020) studied teens with Down syndrome and found extra body fat drove sharp jumps in common inflammation markers. The adult study shows the opposite pattern: alpha2 macroglobulin rises without any inflammation surge. Age and diagnosis may change how inflammation behaves.
McQuaid et al. (2024) showed that chubby adults with Down syndrome usually escape the expected diabetes and cholesterol trouble. Together the two papers paint the same picture: Down syndrome can break the usual rules that link body or mood problems to standard metabolic or inflammation signals.
Why it matters
You now have a quick lab clue. If an adult with Down syndrome shows withdrawal or hallucinations, a high alpha2 macroglobulin with normal CRP can support a depression diagnosis. No spike in classic inflammation does not rule depression out in this group.
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02At a glance
03Original abstract
Studies of immune function during depression in persons without intellectual disability (ID) have revealed elevated levels of alpha2 macroglobulin (alpha2M) and an acute phase protein (APP) response. Clinical observation suggests that people with Down's syndrome (DS) may have associated genetic abnormalities in their immune systems. The APP response and alpha2M changes in depressed versus non-depressed adults with DS was the subject of the present study. The serum pan-proteinase inhibitor alpha2M, and the AP proteins c-reactive protein (CRP), alpha1 antitrypsin (alpha1AT), ceruloplasmin (Cp), beta2 Macroglobulin (beta2M), transthyretin (Trans), serum amyloid protein (SAP), and albumin (Alb) were measured in 38 adults with DS, 19 of whom were diagnosed with and 19 without depression using a sandwich enzyme-linked immunosorbent assay (ELISA). The DSM-IV criteria were used for diagnoses. Medical and neurological examinations excluded medical disorders associated with APP response. Only alpha2M and CRP were significantly different in the depressed versus non-depressed groups. The alpha2M was higher, a response similar to one observed in depressed people without ID, but the CRP was lower in the depressed group, especially in those subjects not on psychotropic medications, contrary to the expected APP response to depression. The results suggest that alpha2M elevation in depressed adults with DS is independent of the APP response. An alternative explanation for its elevation is proposed linking the core symptom of depression with the mammalian dormancy/hibernation process. Further studies are needed to confirm that alpha2M elevation is specific to depression and that it might provide a helpful marker for the diagnosis of depression in people with ID.
Journal of intellectual disability research : JIDR, 2000 · doi:10.1046/j.1365-2788.2000.00287.x