infiltrate

verb

1. (ambitransitive)To surreptitiously penetrate, enter or gain access to.

   “The spy infiltrated the high-tech company and stole many secrets.”

   “Caithness was infiltrated with a palpable sense of being underimagined.”

2. (transitive)To cause to penetrate in this way.

   “The agency infiltrated several spies into the company.”

3. (ambitransitive)To pass through something by filtration.
4. (transitive)To cause (a liquid) to pass through something by filtration.
5. (ambitransitive)To invade or penetrate a tissue or organ.

   “High-grade tumors often infiltrate surrounding structures.”

   “In certain conditions, immune cells may infiltrate into the cerebrospinal fluid.”

   “Plesner et al. reported the nonbeta islet endocrine cell remodeling in diabetic NOD mice: that study suggested that infiltrating immune cells may restrict alpha-cell expansion in NOD mouse islet in the diabetic state [ 36 ].”

6. (transitive)To send (soldiers, spies, etc.) through gaps in the enemy line.
7. (intransitive)To move from a vein, remaining in the body.

noun

1. Any undesirable substance or group of cells that has made its way into part of the body.

   “One critical distinction to make is whether a focal corneal infiltrate is infected with bacteria or is a sterile immunologic response.”

   “Extensive lumpy infiltrates with a tendency to caseate and to form fistulas with purulent secretions appear, mainly in the anogenital region.”

   “Common immunohistochemical markers of this lymphoma include CD2, CD56, CD3, and T-cell receptors. 7 Typically, the histology of these lymphomas are characterized by monomorphic inflammatory cellular infiltrates, which may be diffuse or show angiocentricity and angiodestruction as well as tissue destruction. 7 Lymphoid markers from the nasal mucosal biopsy from this patient were negative for CD56 and EBER.”