Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 146

Lymphoid tissue inducer cells express cytokines TNFSF2 and TNFSF3 138 that
form TNFSF2-TNFSF3 2 complexes. 139 They then activates local stromal cells via
the TNFRSF3 receptor [ 274 ].
Developing lymph nodes collect CD4

cells that
can differentiate into antigen-presenting cells and NK-like cells, but not into B and
T cells [ 272 ]. LTi cells stimulate lymph node formation via LTi cell-stromal cell
clustering. Subsequent binding of TNFRSF3 receptor on stroma-organizer cells to
TNFSF2-TNFSF3 2 heterotrimer on LTi cells upregulates expression of adhesion
molecules, such as VCAM1, ICAM1, and MAdCAM1. Moreover, this binding
provokes the secretion of many chemokines (CXCL13, CCL19 and CCL21).
Consequently, hematopoietic cells, such as B and T cells and dendritic cells, are
recruited to form the lymph node.
In humans, LTi cells have been detected in fetal mesenteric lymph nodes.
They synthesize the transcriptional regulators ID2 (or bHLHb26) and ROR

+ ,CD3 − , TNFSF2 + , TNFSF3 +

2
(or NR1f3-2) as well as several types of plasmalemmal antigens (e.g., CD117, or
SCFR, and CD127, or IL7R

γ

chain). Fetal LTi cells may persist after birth. Postnatal
LTi cells are involved in the formation of isolated lymphoid follicles in the gut in
response to pathogen-associated patterns as well as in repair of damaged lymph
nodes after acute viral infection, at least in adult mice [ 272 ]. In addition, LTi cells
communicate not only with stromal cells, but also with other immunocytes.

α

3.11.2 ILC17 Cells

IL17-producing ILC cells reside mainly in the intestinal tract, especially the colon.
They express and require ROR (NR1f3) for development and function [ 272 ].

Production of IL17 by ILC17 cells is regulated by IL23 cytokine. 140

γ

ILC17 cells

are recruited to the inflammed intestine.
ILC17 cells have a CD4 − , CD117 − (SCFR), NCR1 − phenotype. They can then

be distinguished from CD4 ILC22 cells. ILC17

cells also express thymocyte differentiation antigen Thy1 (CD90), which is also
produced by NK and ILC22 cells.

+ , CD117 + LTi cells and NCR1 +

138 A.k.a. lymphotoxins LT

, respectively.
139 Secreted protein TNFSF2 forms a homotrimer. Transmembrane protein TNFSF3 anchors to the
cell surface the TNFSF2-TNFSF3 complex. The predominant form of surfacic TNFSF2-TNFSF3
heterotrimer is the TNFSF2-TNFSF3 2 heterotrimer.
140 In humans, fetal CD117

α and LT β

+ +

LTi cells also express IL17, but LTi cells express mostly
IL22 and very little IL17 in the postnatal tonsil.

, CD127