The Th1/Th2 paradigm in ocular allergy.
OBJECTIVE
The paradigm that diseases are either Th1 mediated or Th2 mediated has recently been challenged in a number of classical ocular diseases. The objective of this article is to highlight the importance of understanding the exact mechanisms of Th1 and Th2 cells in the pathology of ocular allergy.


RESULTS
Current research of Th1 and Th2 cytokines in an animal model of ocular allergy demonstrates the intricate complex regulation by both subsets of cytokines of the disease process. Th2 prone BALB/c wild type mice sensitized and topically challenged with short ragweed for seven consecutive days (multi-hit) developed a sustained, chronic conjunctival inflammation. Significantly, IFN-gamma knockout mice in the multi-hit antigen challenge model had a reduced conjunctival cellular infiltrate. Evaluation of adhesion molecules that actively regulate cellular infiltration into the conjunctiva revealed a lack of vascular cell adhesion molecule-1 in multi-hit antigen challenged IFN-gamma knockout mice.


CONCLUSIONS
Recent ocular allergy studies question the Th1/Th2 paradigm. These studies encourage further understanding of the intricate interactions of Th1 and Th2 cytokines in ocular inflammatory disease. The following components of Th1 and Th2 cells in the development of chronic inflammation associated with allergic conjunctivitis will be discussed: T helper subsets Th1 and Th2 in ocular inflammation, activation of T cells in the lymph node, and the role of IFN-gamma as the endothelium gatekeeper in the pathology of Th2-mediated allergic conjunctivitis.
Stern
Michael E
ME
Department of Biological Sciences, Allergan, Inc., Irvine, California, USA. Stern_Michael@allergan.com
Siemasko
Karyn F
KF
Niederkorn
Jerry Y
JY
D000818:Animals; D015815:Cell Adhesion Molecules / Q000276:immunology; D003228:Conjunctiva / Q000276:immunology; D003233:Conjunctivitis, Allergic / Q000276:immunology* / Q000473:pathology; D016207:Cytokines / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology*
D015815:Cell Adhesion Molecules; D016207:Cytokines; D007371:Interferon-gamma