**Part 1**

**Pathophysiology** 

**1** 

 *China* 

**Psoriasis and Stem Cells** 

Kaiming Zhang, Guohua Yin, Xinhua Li,

*1 Dong San Dao Xiang, Taiyuan, Shanxi Province,* 

Xuping Niu, Ruixia Hou, Ruifeng Liu and Junqin Li

*Taiyuan City Central Hospital Affiliated to Shanxi Medical University,* 

Psoriasis is a chronic inflammatory skin disorder characterized by hyper-proliferation of basal keratinocytes, thickened and scaly epidermis, and recruitment of inflammatory cells to the skin. It affects approximately 2% of the world's population. The disease follows a pathogenic pathway involving various immunocytes and immune molecules. Activated T cells have been shown to trigger a chain of cellular and molecular reactions leading to the formation of psoriatic lesions. Fusion proteins that can block T cell activation or the function of anergized T cells, and cytokines and biologics that can inhibit T cell migration are effective in the treatment of psoriasis. Intradermal injection of T cells from psoriatic patients into human skin/severe combined immunodeficient (SCID) mice can induce spontaneous psoriatic conversion of skins from healthy human or non-lesional skin from psoriatic patients. Thus, it is widely accepted that psoriasis is a T lymphocyte-mediated autoimmune disease. Although the roles of T cells in psoriasis have been confirmed, the exact

Beside T cells, psoriatic patients have a wide variety of other immune abnormalities such as B cells, monocytes, neutrophils and erythrocytes. As the precursor of immune cells, bone marrow hematopoietic stem cells have been suggested to be responsible for immune dysregulation of T cells in psoriasis. Several recent studies have indicated that abnormal T cells may be closely related to anomalous hematopoietic stem cells (HSCs) determined by psoriatic hereditary background. In addition to HSCs, aberrant bone marrow mesenchymal

**2. The clinical cue of relationship between psoriasis and bone marrow cells**  Although various exogenous and endogenous factors are believed to activate the immune system leading to imbalance of the system and initiation of psoriasis, increasing evidences suggest that inherent and intrinsic rather than extrinsic factors are more important in psoriasis pathogenesis. These intrinsic factors may be involved in spontaneous T-cell activation or proliferation, regulation of cytokine production, hematopoietic cell development, and T-cell development in the thymus. Allogeneic bone marrow transplantations (BMT) have been reported to either eliminate or aggravate psoriasis.

mechanisms of psoriasis and the origin of abnormal T cells are still unclear.

stem cells have also been demonstrated in patients with psoriasis.

**1. Introduction** 
