Table. Demographics, Diagnostics, and Neuronal Surface Autoantibodies Test Results by Different Methods.
| Characteristic | Control Participantsa | Individuals With Psychotic Disorders | Individuals With Subdiagnoses of Psychotic Disorders, No. (%) | ||||
|---|---|---|---|---|---|---|---|
| Schizophrenia | Schizoaffective Disorder | Brief Psychotic Disorder | First-Episode Psychosis | Other Psychotic Diagnoses | |||
| Total, No.b | 257 | 621 | 476 | 44 | 38 | 45 | 18 |
| Mean (SD) age, y | 44.1 (16.6) | 34.4 (11.9) | 36.6 (11.9) | 31.5 (7.9) | 26.7 (7.9) | 22.2 (5.6) | 32.4 (10.2) |
| Female | 122 (47.5) | 248 (39.9) | 188 (39.5) | 27 (61.4) | 13 (34.2) | 16 (35.6) | 4 (22.2) |
| Grade, No. (%) | |||||||
| 1 | 14 (5.4) | 40 (6.4) | 29 (6.1) | 4 (9.1) | 2 (5.3) | 2 (4.4) | 3 (16.7) |
| 2 | 8 (3.1) | 13 (2.1) | 10 (2.1) | 2 (4.5) | 1 (2.6) | 0 | 0 |
| 3c | 5 (1.9) | 14 (2.3) | 10 (2.1) | 1 (2.3) | 2 (5.3) | 1 (2.2) | 0 |
| Cell-based assaysd | |||||||
| Tested, No. | 27 | 67 | 49 | 7 | 5 | 3 | 3 |
| Caspr2, live | 3 | 3 | 2 | 0 | 1 | 0 | 0 |
| Othere | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Live neurons, No. | |||||||
| Tested | 5 | 14 | 10 | 1 | 2 | 1 | 0 |
| Positive | 1 | 1 | 1 | 0 | 0 | 0 | 0 |
Abbreviations: Caspr2, contactin-associated protein-like 2; IHC, immunohistochemistry.
Control participants consisted of 200 individuals who had donated blood and 57 individuals who were without a psychiatric diagnosis.
All cases with grade 1 to 3 by IHC testing were further tested by cell-based assays to determine the existence of antibodies to known neuronal surface antigens.
All cases with grade 3 by IHC testing were further tested by live neurons to characterize if they target to unknown neuronal surface antigens.
In-house cell-based assays were used for the following antigens: N-methyl-d-aspartate receptor 1 (alone and GluN1/GluN2B), leucine-rich glioma-inactivated 1, Caspr2, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, and γ-aminobutyric acid receptor subunit A and B. Human embryonic kidney (HEK) 293 cells were transfected with 4 μg of expression vectors for the respective human sequences. Cells were fixed in formaldehyde, 3.6%, for 10 minutes and permeabilized with Triton-X-100, 0.3%, for 10 minutes. After blocking with bovine serum albumin, 1%, for 1 hour, cells were incubated with human sera diluted 1:40 in albumin, 1%, together with an antibody targeting the according antigen for 1 hour at room temperature. Cover glasses were mounted onto 7 μL of 4′,6-diamidino-2-phenylindole mounting medium and evaluated by 2 observers (of whom 1 was blinded) independently on a BX51 microscope (Olympus) for antibody reactivity. When results were positive, the staining was repeated with serial dilution (1:50 up to 1:3200). Live cell-based assays were performed for all 6 neuronal surface antibodies as described for the fixed cell-based assay, with small modifications. In these cases, HEK293 cells were grown and transfected as described, with the difference that antigens were expressed with fluorescent reporter proteins, if available (leucine-rich glioma-inactivated 1–green fluorescent protein, N-methyl-d-aspartate receptor 1–green fluorescent protein, and Caspr2-mCherry). Human serum was incubated, diluted 1:50 in Dulbecco modified Eagle medium with bovine serum albumin, 1%, and 25mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid at room temperature for 1 hour, and fixed in formaldehyde, 3.6%. The secondary antibodies were incubated without additional permeabilization or blocking steps. Mounting and analysis was done as for the fixed cell-based assays.
Tests in this category included live and fixed cell-based assays for detecting antibodies to N-methyl-d-aspartate receptor, α-amino-3 hydroxy-5-methyl-4-isoxazolepropionic acid receptor, γ-aminobutyric acid receptor subunits A and B, leucine-rich glioma-inactivated 1, and a fixed cell-based assay for antibodies to Caspr2.