# Case study: Xenium: the ligand-receptor pair that was segmentation leakage
URL: https://omicsquest.com/case-studies/xenium-segmentation-leakage/

T cells appeared to express a myeloid ligand and its receptor at once, suggesting autocrine signaling. It was transcript spillover from adjacent cells.

Problem: The lab saw CD4 T cells that expressed both a chemokine normally made by dendritic cells and its receptor, and planned follow-up experiments on autocrine signaling. Expression was patchy and strongest where T cells touched dendritic cells.

Findings:
- Default nuclear expansion of 5 µm in densely packed T-cell zones meant neighboring cells' transcripts were assigned to T cells.
- Mutually exclusive marker pairs (CD3E with ITGAX or LYZ) co-occurred in 14% of T cells, a direct measure of segmentation error.
- The 'autocrine' ligand transcripts sat at the cell periphery facing dendritic cells, not in the T-cell cytoplasm.

Rescue:
- Re-segmented with Proseg and compared it with Baysor, using membrane stain where available.
- Quantified mixing before and after with exclusive-marker co-expression rates.
- Re-annotated cells and re-ran neighborhood and ligand-receptor analysis restricted to true neighbors.

Result: Exclusive-marker co-expression dropped from 14% to under 3%. The autocrine signal disappeared, and a clear paracrine dendritic-cell-to-T-cell axis emerged at the T-B border. The lab redirected its validation experiments before spending months on the wrong hypothesis.

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Source: https://omicsquest.com/case-studies/xenium-segmentation-leakage/ | OmicsQuest, contact@omicsquest.com