Morula forms of E rosettes: distribution, specific inhibition, and enhancement

Area of Science:

• Immunology
• Cell Biology

Background:

• Rosette-forming cells (RFC) are crucial in immune responses.
• Morula-forming cells (MFC) are a specific type of RFC characterized by binding >10 sheep red blood cells (SRBCs).

Purpose of the Study:

• To investigate the distribution and characteristics of MFC in human lymphoid organs and peripheral blood.
• To explore the role of MFC in immune function and their association with specific clinical conditions.

Main Methods:

• Studied MFC frequency in thymus, peripheral lymphoid tissues, and peripheral blood (PBL) across different age groups.
• Utilized antisera (antihuman thymus, anti-human lymphoblastic, normal brain, anti-IgM, anti-L chain) to assess MFC characteristics.
• Analyzed MFC ratios in patients with chronic lymphocytic leukemia (CLL) and thymic deficiency.
• Investigated MFC changes after phytohemagglutinin (PHA) stimulation and other treatments.

Main Results:

• MFC constitute over 50% of RFC in the thymus, with lower frequencies in PBL (29.8% in <5 years, 14.9% in adults).
• Antihuman thymus antiserum (ATS) and anti-human lymphoblastic antiserum (ATL) significantly inhibited both total RFC and MFC formation.
• No inhibition was observed with normal brain, anti-IgM, or anti-L chain antisera.
• Elevated MFC to RFC ratios were noted in CLL patients and those with thymic deficiency.
• MFC numbers increased after PHA culture, blast transformation, or surface perturbation (papain, freeze-thaw).

Conclusions:

• MFC represent a distinct population of immune cells, primarily found in the thymus.
• MFC characteristics suggest a T-cell lineage involvement, potentially related to lymphoblastic cells.
• The altered MFC ratio in CLL and thymic deficiency indicates a potential diagnostic or prognostic marker.
• MFC are sensitive to activation and surface changes, highlighting their dynamic nature in immune responses.