The objective of this study is to estimate the possible role of CD184 in the pathogenesis of SLE; comparing its level among SLE cases to healthy controls.

Detection of CXCR4 (CD184) expression on CD19+ B cells by flow cytometry in patients of SLE, comparing its level in the development of lupus activity and pathogenic process of SLE internal organ involvement/ mucocutaneus and/or musculoskeletal involvement. Identify this correlation will be useful for clarifying other accessory factors to improve the diagnosis, better treatment strategy, follow up as well as prognosis for these patients

Inclusion Criteria:

• Confirmed SLE patients diagnosed and fulfilled the SLE classification criteria according to the 2019 ACR/EULAR classification criteria for SLE (Aringer et al., 2019)
• Willing and agreed to be included in the study.

Exclusion Criteria:

• Childhood SLE.
• SLE-patients will refuse to consent to this study.
• Other autoimmune diseases.
• Known or suspected malignancies, especially B cell lymphoma.

Study population will be classified into two group:

1. SLE patients group: Confirmed SLE patients diagnosed and fulfilled the SLE classification criteria according to the 2019 ACR/EULAR classification criteria for SLE (Aringer et al., 2019).
2. Control group: Healthy age and sex matched subjects.

Then SLE group I patients will be subdivided according to the disease activity to three subgroups:

I. Group A: SLE cases in remission II. Group B: SLE cases in activity, but no internal organ involvement (i.e. only mucocutaneus and/or musculoskeletal involvement).

III. Group C: SLE cases in activity, and with internal organ involvement (renal, neuropsychiatric, hematological or cardiopulmonary).