Immunological profiles in Inflammatory Bowel Disease

Inflammatory Bowel Diseases (IBD) is a heterogeneous group of diseases
regarding clinical presentation and treatment response. Incidence is increasing
and disease burden is high due to the young age at onset and the chronic nature
of the disease. Pathogenesis is complex and multifactorial based on
interactions between genetic and environmental factors, gut microbiota and the
immune system, leading to intestinal inflammation.

Alterations in T-cell subsets and homing of lymphocytes to gut mucosa were
shown to play an important role in the pathogenesis of IBD1, causing
inflammation primarily in the intestine but also in extra-intestinal tissues.
The therapeutic arsenal is directed to suppress this immune mediated
inflammatory reaction.
We previously reported different T-cell maturation profiles in the ileum/colon
mucosa of newly diagnosed IBD patients which consist of mainly naïve T cells
(Tn cells) and central memory T cells (Tcm cells) versus mainly effector memory
T cells (Tem cells). Higher frequencies of Tn cells in patients with Crohn*s
Disease (CD) were associated with a more extended and penetrating disease,
reflecting a more aggressive initial presentation.2 Furthermore we recently
identified several serum markers associated with disease activity and disease
course (s-TNF R1, s-TNFR2, sIL2R, MMP1) in newly diagnosed Crohn*s disease
patients.3

Migration of Tn * and Tcm cells to the gut is thought to be facilitated by
tertiary lymphoid organs (TLOs) containing high endothelial venules (HEVs). The
migration of T cells through HEVs is guided by different vascular addressins,
such as MAdCAM-1 and peripheral lymph node addressin (PNAd). Differences in
HEVs density and TLOs between newly diagnosed IBD patient with active disease
has been recently described.4 Increased density of colonic extrafollicular HEVs
in the early phase of disease was associated with more Tn- and Tcm cells in the
inflamed gut mucosa, which could be responsible for maintaining a continuous
inflammatory process.

These differences in the early phase of IBD seem to be mechanistically
associated with different migration patterns of T cells into the gut mucosa and
might explain the differences in response to therapy with biologicals. Karlsson
et.al. (2014)5 showed a decrease in Tn and effector memory T cells
re-expressing CD45RA in the gut mucosa with effective treatment
(corticosteroids or biologicals), whereas memory T cells remained unchanged.
The formation and development of TLOs in other different chronic immune
mediated disorders (e.g. rheumatoid arthritis) and malignancies has been found
to play an important role in local immunological dysregulation and showed
predictive value for disease course (longer duration) and response to therapy.
In patients with rheumatoid arthritis, TLOs were associated with inferior
response to anti-TNF treatment and resolution of TLOs was shown to be a good
marker of therapeutic response.6

The roles of CTLA-4 and PD-1 in inhibiting immune responses have recently
gained attention. CTLA-4 is thought to regulate T-cell proliferation early in
the immune response, primarily in lymph nodes. PD-1 suppresses T cells later in
the immune response, primarily in peripheral tissues. Inhibition of CTLA-4
(ipilimumab) and PD-1 (nivolumab) can restore antitumor immune responses
leading to long-term benefit in a substantial proportion of treated patients.7
Blockade of CTLA-4 activates a large repertoire of T cells, not only
tumour-specific T cells. Patients treated with ipilimumab and nivolumab often
develop immune-related events such as enterocolitis which is the most frequent
immune-related adverse event suggesting a role for CTLA-4 and PD-1 in the
pathogenesis of IBD. 8

In the present, diagnosis is based on a combination of internationally accepted
clinical, endoscopic, histological and radiological findings. Biomarkers as
CRP, ESR, faecal calprotectin and pANCAs can only be used as an adjunct to
endoscopic evaluation or in monitoring disease activity. Unless wide
differences in disease course between IBD patients, up till now no biomarkers
have been identified with predictive value for this course.9,10,11

At present patients are systematically treated using a step up treatment
strategy according to the Dutch Guidelines IBD, including steroids, thiopurines
and in case of steroid refractory or steroid dependent disease the use of
biologicals e.g. anti-TNF. The described immunologic differences between IBD
patients at the moment of diagnosis might explain the heterogeneity in response
to different medications. These immunological characteristics may enable
targeting with more specific medication. Treatment strategy would be more
rational and individuals could get more personalised effective treatment
without delay.

Primary Objective:
1. Determine if assessment of mucosal and serological immunological
characteristics in combination with clinical indicators of disease behaviour
and response to therapy can identify immune-based phenotypes with implications
for prognosis and therapeutic interventions.

Secondary Objective(s):
2. Determine the presence of HEVs/TLOs and T cell subsets in the mucosa of IBD
patients at presentation and during follow-up and associate this to clinical
phenotypes and treatment response.
3. Analyse the amount of regulatory T cells in combination with PD-1 and CTLA-4
in the mucosa and serum of IBD patients and healthy controls.
4. Determine differences in levels of chemokines and cytokines in serum and
mucosa in IBD patients and healthy controls at baseline and during follow-up.

The study will be a longitudinal, prospective cohort study that will be
performed at the Departments of Gastro-enterology and Hepatology, Microbiology
and Immunology and Pathology of the Rijnstate Hospital in Arnhem. The patients
will undergo diagnostic procedures and treatment according to the standard
clinical practice.

Ileocolonoscopy with biopsies is a standard examination in patients presenting
with chronic (+/- bloody) diarrhoea and in the follow up of patients with IBD.
Collection of biopsies during the gastroenterological endoscopy, ie without
interventions like polypectomy, is a safe procedure (bleeding, perforation
<0,001). In the regular clinical practice, different endoscopists take a
variable number of biopsies (4-10) from sites of interest. The intervention in
this study comprises taking 4 additional biopsies on top of the regular
histological biopsies for immunological examination.
Before ileocolonoscopy, patients normally receive an infusion needle for the
administration of sedation (standard care). After ileocolonoscopy this needle
will be used to take a venous blood sample. If this is not possible, we take a
venous bloodsample during a regular labcontrol. In the follow up period, during
regular endoscopies and blood checks the same additional samples will be taken.
Therefore, we believe the burden and risks for patients are minimalised.