Author

Findings

Antibody Target

Cohort

Warren et al. (1990)^[1]

6 of 11 mothers with an autistic child had antibodies reactive to lymphocytes of the child.

Human lymphocytes

MAU = 11
All mothers had an autistic child 6 years of age or younger.
Plasma samples taken after recruitment

Since lymphocyte antigens can be shared with neuronal antigens, the study indicated that maternal antibodies might be associated with the development of autism.

Barnes et al. (1995)^[2]

Four children with AMC born to an initially asymptomatic mother and separate unrelated fathers
The mother developed muscle weakness following her first pregnancy and was diagnosed with MG after her fourth.

Unclear at this stage

1 mother with 4 pregnancies affected by AMC and a subsequent diagnosis of MG

It was striking that the diagnosis of AMC was made only after the fourth affected child.
A very high risk of recurrence in maternal MG-associated AMC is evident (also in Vincent et al., 1995).

Vincent et al. (1995)^[3] and Riemersma et al. (1997)^[4]

Serum from a mother of children affected by a neuromuscular disorder contained a high titre of antibodies that selectively inhibited the foetal form of acetylcholine receptor.

Acetylcholine receptors (antibodies inhibiting function of foetal isoform)

1 healthy mother with 6 consecutive pregnancies affected by AMC
Serum was taken before the 6^th pregnancy.

First study to implicate clearly maternal antibodies as a cause of developmental disorder in the children of unaffected mothers
Implications for a pathogenic role of the maternal antibodies:
1. Recurrence of AMC in 6 pregnancies makes a genetic cause unlikely.
2. Foetal movements were observed in the pregnancies until 15–18 weeks, the time at which foetal IgG levels begin to rise rapidly.
3. Repeated plasma exchange from 10 weeks gestation prolonged foetal movements.

Zimmerman et al. (2007)^[5]

Antibodies in the serum of mothers of autistic children recognised different foetal but not adult rat brain proteins compared to controls.

Adult and foetal rat brain protein preparations

MAU = 11
MTD = 10
Plasma samples taken after recruitment

Western blotting procedure as in numerous following studies:
1. Brain protein preparation was gel electrophoresed, then transferred onto nitrocellulose membrane.
2. Nitrocellulose membranes were incubated in maternal plasma, then incubated with secondary antibody before imaging.
Crude membrane proteins are not ideal as the they expose both intracellular and extracellular sequences, and also gel electrophoresis requires denaturation of the proteins.

Braunschweig et al. (2008)^[6]

Increased plasma reactivity to 37 kDa band in mothers of autistic children
Paired reactivity to 37 and 73 kDa bands found exclusively in mothers of autistic children

Foetal human brain protein preparation

MAU = 61
Controls:
MTD = 62
MDD = 40
Plasma samples taken after recruitment

There is inconsistency in the bands identified by the five immunoblotting studies.
However, when results from Braunschweig’s 2008 and 2012 studies are combined, the 37/73 kDa band pattern achieves a highly specific association with ASD, yielding an odds ratio of 39.4.

Croen et al. (2008)^[7]

Increased plasma reactivity to a 39 kDa band in mothers of autistic children
Paired reactivity to 37 and 73 kDa bands found exclusively in mothers of children with early onset autism

Foetal human brain protein preparation

MAU = 84
Controls:
MTD = 160
MDD = 49
Plasma samples taken after recruitment

Singer et al. (2008)^[8]

Increased plasma reactivity to 36, 39, 61 and 73 kDa bands in mothers of autistic children

Human and rat foetal brain protein preparation

MAU = 100
MTD = 100
Plasma samples taken after recruitment

Braunschweig et al. (2012)^[9]

Increased plasma reactivity to 37, 39 and 73 kDa bands in mothers of autistic children
37/73 kDa paired reactivity strongly increased in mothers of autistic children

Foetal monkey brain protein preparation

MAU = 272
Controls:
MTD = 185
MDD = 102
Plasma samples taken after recruitment

Braunschweig et al. (2013)^[10]

Tandem mass spectrometry and peptide sequencing were used to identify antigen candidates for 37, 39, 73, 70 and 44 kDa proteins. LDH, YBX1, cypin, STIP1, CRMP1 and CRMP2 were confirmed as autoantibody targets in binding inhibition Western blot studies.

Foetal monkey brain protein preparation

MAU = 246
MTD = 149
Plasma samples taken after recruitment

Brimberg et al. (2013)^[11]

Plasmas from mothers of autistic children were four times more likely to contain anti-brain antibodies than control plasmas (10.5% vs. 2.6%).

Mouse brain sections

MAU = 2431
MTD = 653
Plasma samples were from blood banks and not mid-gestational.

First large cohort study and thus important evidence that mothers of an autistic child have an elevated frequency of anti-brain antibodies
Most reliable indicator of the incidence of MAR autism

Brimberg et al. (2016)^[12]

Plasma reactivity to CASPR2 was found in 37% of ASD mothers displaying brain-reactive serology compared to 12% of ASD mothers lacking brain-reactive serology.

Mouse brain in vivo
Caspr2-transfected HEK-293T cells

MAU with reactive serology = 53
MAU lacking reactive serology = 63
Plasma samples as above

Coutinho et al. (April 2017)^[13]

CASPR2-Abs found more frequently in mothers of children with MR/DPD (7/171; 4%) than control mothers (1/171; 1%)
No excess of CASPR2-Abs in mothers of children with autism (1/95; 1.1%) compared to control mothers (2/95; 2.1%).
No excess of NMDAR antibodies compared to controls in mothers of children with neurodevelopmental disorders (10/171; 4% vs. 9/171; 5%) or autism (2/95; 2% vs. 3/95; 3%).

Live human embryonic kidney cells transfected with cDNA encoding CASPR2 or NMDAR

Gestational week 14–18 mothers of children with mild or unspecified neurodevelopmental disorders (n = 171, cases) and mothers whose child had not received this diagnosis (n = 171, controls)
Gestational week 14–18 mothers of children with ASD (n = 95, cases) and mothers whose child had not received this diagnosis (n = 95, controls)
Serum samples from the pregnancy screening biobank at the Danish State Serum Institute

Jurek et al. (2019)^[14]

Mothers of children with psychiatric disorders had slightly higher titres of NR1-reactive IgG compared to mothers of unaffected children.

Live HEK cells over-expressing native human NR1 protein

120 healthy mothers of children with psychiatric disorders; 105 healthy control mothers of unaffected children
Plasma samples taken 4–20 years after the pregnancy

No association with any specific psychiatric disorder

Author

Findings

Cohort

Jacobson et al. (1999)^[15]

Plasma from four AChR antibody-positive women injected into pregnant mouse dams: foetuses displayed deformities resembling AMC.

4 AChR antibody-positive women with histories of severe AMC in their babies
Control plasma obtained from healthy laboratory workers (including 3 women with recent pregnancies) and therapeutic plasma exchange (other neurological diseases control)

First to establish passive transfer animal model for study of maternal antibody-mediated developmental disorder

Dalton et al. (2003)^[16]

Plasma from a mother of an autistic child and a child with a severe specific language disorder injected into pregnant mouse dams: offspring displayed a slowed righting reflex, decreased exploration and decreased performance on the multiple static rods test.

1 mother of 3 children: 1 TD, 1 with autism and 1 with a severe specific language disorder;
4 mothers with between 1 and 4 typically developing children;
Plasma samples taken after recruitment

First causative study indicating that maternal factor can induce behavioural disorder in offspring

Martin et al. (2008)^[17]

Prenatal exposure to purified pooled IgG from mothers of autistic children produced stereotypies and hyperactivity in rhesus macaques.

MAU = 21
All mothers had at least two children with autism;
MTD = 7
All mothers had at least two typically developing children;
Plasma samples taken after recruitment

No changes in sociability were observed. However, the changes observed are particularly compelling in a primate model.

Lee et al. (2009)^[18]

NMDAR (NR2) immunisation, with NMDAR antibodies present before and throughout gestation
NMDAR antibody-exposed E15 foetuses displayed histological brain abnormalities, including cortical thinning, which persisted into adulthood in offspring of dams with high titres.
These pups were slow to develop the negative geotaxis reflex. When adult offspring were impaired in fear extinction, novel object recognition and topological tasks.

Antibodies in this model cross-reacted with NR2A and NR2B. However, mouse NR2A expression is thought to be strictly postnatal so the observed phenotype was most likely due to antibodies targeting NR2B. In humans, NR2A expression has been detected in the foetal neocortex.
Supports a role for NMDAR antibodies in disruption of foetal cortical development, but relationship to autism not clear

Singer et al. (2009)^[19]

Prenatal exposure to purified pooled IgG from mothers of autistic children produced hyperactivity, sociability alterations and anxiety-like behaviour in mice.

MAU = 63
All children judged to have moderate to severe adaptive or cognitive deficits by formal testing
TD = 63
Plasma samples taken after recruitment

Braunschweig et al. (2012)^[20]

Purified IgG from mothers of autistic children with paired 37/73 kDa band reactivity was injected into pregnant mice: Offspring displayed anxiety-like behaviour and delayed physical and sensory-motor development.

MAU = 3 (selected for paired 37/73 kDa reactivity)
MTD = 3
Plasma samples taken after recruitment

No significant changes in sociability

Bauman et al. (2013)^[21]

Purified IgG from mothers of autistic children with paired 37/73 kDa band reactivity was injected into pregnant rhesus macaques: Offspring were treated with heightened protectiveness by their mothers, and on maturing they displayed increased approach of familiar peers (was not reciprocated and didn’t lead to sustained social interactions) and inappropriate approach of unfamiliar peers. Male offspring also had enlarged brains and increased white matter volume most pronounced in the frontal lobes.

MAU = 4 mothers (selected for paired 37/73 kDa reactivity)
MTD = 5 mothers (selected to lack 37 and 73 kDa reactivity)
Plasma samples taken after recruitment
Plasma samples taken after recruitment

These were very compelling data and the first demonstration of aberrant social development in non-human primates exposed to autism-associated anti-brain antibodies. Increased brain size and white matter volume have been consistently reported in autism^{[22][23][24][25][26][27][28][29]} and have been specifically reported in the MAR autism subtype^[30].
The study was limited by its small sample size (8 macaques received MAU IgG, 8 received control IgG).

Brimberg et al.
(2016)^[12]

Monoclonal C6 (CASPR2 antibody) derived from mother of autistic child injected into pregnant mice: offspring displayed differences in sociability, repetitive behaviour and flexible learning.

Monoclonal CASPR2 derived from 1 mother of an autistic child
Control = Non-brain-reactive human antibody, B1

Martínez-Cerdeño et al. (2016)^[31]

Purified IgG from mothers of autistic children with paired 37/73 kDa band reactivity was injected into pregnant mice: IgG recognised radial glial cells, increased subventricular zone and extra-cortical cell proliferation and increased both the size and weight of adult brains and the size of adult cortical neurons.

MAU = 4 (selected for paired 37/73 kDa reactivity)
MTD = 5 (selected to lack 37 and 73 kDa reactivity)
Plasma samples were from the CHARGE study at the University of California and were taken 1–5 years after pregnancy

Ariza et al. (2017)^[32]

Purified IgG from mothers of autistic children with paired 37/73 kDa band reactivity was injected into pregnant mice: IgG reduced dendritic spine number and density in the frontal and occipital cortices.

MAU = 1 (selected for paired high-titre 37/73 kDa reactivity)
MTD = 1 (selected to lack 37 and 73 kDa reactivity)
Plasma samples were from the CHARGE study at the University of California and were taken 1–5 years after pregnancy

Coutinho et al. (October 2017)^[33]

IgG from two patients with CASPR2-antibody encephalitis injected into pregnant mice: Adult offspring showed social interaction deficits, abnormally located glutamatergic neurons in layers V-VI of the somatosensory cortex, microglial overactivation and a reduction in glutamatergic synaptic profile density in the prefrontal and somatosensory cortices.

2 male patients with CASPR2-antibody encephalitis
3 healthy age- and sex- matched individuals

Jones et al. (2018)^[34]

Antigen-driven model of MAR autism based on the ASD-specific 37/73 kDa band pattern: offspring of immunised dams showed differences in juvenile sociability and repetitive behaviours.

The ELISAs done to confirm antibody generation produced low antibody titres, ranging between 0.3 and 0.5 OD;
No attempt was made to verify that the effect was antibody-mediated rather than the result of formation of inflammatory immune complexes with the peptide antigens.
Mixed results in behavioural tests

Jurek et al. (2019)^[14]

Cloned human antibodies were injected into pregnant mice: Offspring had reduced synaptic NMDAR densities, increased mortality, altered physiological functions during early development (elevated blood pH, reduced weight gain) and impaired neurodevelopment. Behavioural changes persisted into adulthood.

IgG1 cloned from 2 female patients with acute NMDAR encephalitis (obtained during periods of disease exacerbation)
Control = non-brain-reactive human IgG1

Findings could relate to a spectrum of behavioural disorders, not necessarily autism.