IL-2 signaling pathways and regulation
The pleiotropic effects of IL-2 are enabled due to the fact that IL-2 signal can be transduced via 3 different signaling pathways; JAK-STAT, PI3K/Akt/mTOR and MAPK/ERK pathway. After IL-2 binding to its receptor, cytoplasmatic domains of CD122 and CD132 heterodimerize. This leads to the activation of Janus kinases JAK1 and JAK3 which subsequently phosphorylate T338 on CD122. This phosphorylation recruits STAT transcription factors, predominantly STAT5, which dimerize and migrate to the cell nucleus where they bind to DNA.Gene expression regulation for IL-2 can be on multiple levels or by different ways. One of the checkpoints is signaling through TCR, antigen receptor of T-lymphocytes after recognizing MHC-peptide complex. Signaling pathway from TCR then goes through phospholipase-C (PLC) dependent pathway. PLC activates 3 major transcription factors and their pathways: NFAT, NFkB and AP-1. After costimulation from CD28 the optimal activation of expression of IL-2 and these pathways is induced. At the same time Oct-1 is expressed. It helps the activation. Oct1 is expressed in T-lymphocytes and Oct2 is induced after cell activation. NFAT has multiple family members, all of them are located in cytoplasm and signaling goes through calcineurin, NFAT is dephosphorylated and therefore translocated to the nucleus. AP-1 is a dimer and is composed of c-Jun and c-Fos proteins. It cooperates with other transcription factors including NFkB and Oct.
NFkB is translocated to the nucleus after costimulation through CD28. NFkB is a heterodimer and there are two binding sites on the IL-2 promoter.
The cranial nerves affected are (from most common to least common) : VIII (cochlear component), VIII (vestibular component), V

Acoustic neuroma/vestibular schwannoma
Meningioma, a tumor of the meninges or membranes that surround the nerves passing through the CPA
Cerebellar astrocytoma, a malignant tumor of star-shaped glial cells called astrocytes in the cerebellum
Intracranial epidermoid cyst
Lipoma
Glomus jugulare associated with the glossopharyngeal nerve
Idiopathic hypertrophic pachymeningitis
IgG4-related hypertrophic pachymeningitis
CPA Metastases in cancer patients with inner ear symptoms (rare)

Diagnosis
Radiography
Subsequent to diagnosis of sensorineural hearing loss, and differential diagnosis of retrocochlear or neural etiologies,
radiological assessment of the CPA is performed to assess the presence of anatomical retrocochlear lesions. Traditional protocols
Before the advent of MRI, electronystagmography and Computed Tomography were employed for diagnosis of acoustic neuroma. Auditory brainstem response audiometry and adjunct tests
The auditory brainstem response (ABR) test gives information about the inner ear (cochlea) and nerve pathways for hearing via ongoing electrical activity in the brain measured by electrodes placed on the scalp. Five different waves (I to V) are measured for each ear. Each waveform represents specific anatomical points along the auditory neural pathway. Delays of one side relative to the other suggest a lesion in cranial nerve VIII between the ear and brainstem or in the brainstem itself. The most reliable indicator for acoustic neuromas from the ABR is the interaural latency differences in wave V: the latency in the impaired ear is prolonged. Different studies have indicated the sensitivity of ABR for detection of acoustic neuromas 1cm or larger to be between 90 and 95%. Sensitivity for neuromas smaller than 1cm are 63-77%.