Circulating immune profile in patients with amyloidosis Free

Introduction Although both light-chain (AL) and transthyretin (ATTR) amyloidosis involve accumulation of misfolded proteins in one or more organs, these conditions have different origins. Whereas AL is an immune disorder caused by abnormal plasma cells in the bone marrow releasing amyloidogenic immunoglobulin light chains, ATTR is caused by deposition of misfolded TTR protein, which is normally involved in transporting thyroid hormone and retinol. Little work has been done to examine the immune profiles of patients with AL vs ATTR.

Methods Flow cytometry was utilized to assess the peripheral blood frequency of lymphocyte populations and subsets. The current analysis reports differences between groups of treatment-naïve patients with AL or ATTR, and patients with either a negative amyloidosis workup and no other plasma cell disorder, or healthy donors. Statistical analyses include linear regressions with the continuous immune marker as the dependent variable, and age, sex, and diagnosis as the independent variables. Immune markers with significant (p≤.05) regression coefficients on the diagnosis parameter are reported. The false discovery rate (FDR) is controlled using the Benjamini-Hochberg procedure.

Results The study sample includes 101 people with amyloidosis (AL: n=58; ATTR: n=43), 83 negative for amyloidosis, and 97 healthy donors, having a mean age of 62.4 years and a majority of females (59.8%).

Amyloidosis vs Negative: Compared to patients with a negative amyloidosis workup, patients with AL or ATTR have a more activated, exhausted, and terminally differentiated lymphocyte profile. Markers that are significantly higher in amyloidosis include: CD4⁺ effector to central memory T cell ratio (TEM/TCM) (amyloidosis); CD8⁺ T cells (ATTR); CD8⁺ TEM (amyloidosis, AL); CD8⁺ total exhausted T cells (amyloidosis, ATTR); CD4⁺ terminally differentiated effector memory T cells (amyloidosis, ATTR); terminally differentiated large granular lymphocytes (amyloidosis, ATTR); and both total and terminally differentiated natural killer T (NKT) cells (ATTR), with larger differences in terminally differentiated. However, terminally differentiated natural killer (NK) cells are lower in AL than negative. None of these differences are significant after FDR correction.

Amyloidosis vs Healthy: Compared to healthy donors, patients with AL or ATTR have a significantly less naïve, more activated, and more terminally differentiated lymphocyte profile, but also a less exhausted helper T cell profile. Markers that are lower in amyloidosis include: CD4/CD8 ratio (ATTR); CD4⁺ T cells (ATTR); CD4⁺ naïve T cells (amyloidosis, AL, ATTR); CD4⁺ T cells expressing two or more exhaustion markers (amyloidosis, AL, ATTR); CD8⁺ naïve T cells (amyloidosis, AL, ATTR); CD8⁺ TCM (ATTR); memory B cells (amyloidosis, AL); non-class switched memory (NCSM) B cells (amyloidosis, AL, ATTR); and NK (amyloidosis, AL). Markers that are higher in amyloidosis include: CD4⁺ TEM to exhausted T cells ratio (AL); CD8⁺ TEM to exhausted T cells ratio (amyloidosis, AL, ATTR); CD8⁺ TEM/TCM ratio (ATTR); and both total and terminally differentiated NKT (ATTR), with larger differences in terminally differentiated. The only significant differences after FDR correction are memory B cells being lower in AL than healthy, and NCSM B cells being lower in amyloidosis, AL, and ATTR than healthy.

ATTR vs AL: Compared head-to-head, only B cells are significantly higher in patients with ATTR than AL, but this difference does not remain significant after FDR correction.

Discussion The current study presents evidence that the immune system in amyloidosis patients differs from that of individuals without amyloidosis, suggesting an immune system that has been heavily antigen-exposed, activated, and primed for effector function, but with less proliferative potential. Some of the greatest differences observed in amyloidosis patients include a substantially greater number of NKT and higher ratio of CD8⁺effector to central memory T cells. Interestingly, CD4⁺ T cells are less exhausted in amyloidosis, while CD8⁺ T cells are more exhausted. However, the strong CD8⁺ effector memory presence suggests an immune system that can still respond to previously encountered antigens. Furthermore, it appears that the immune system in ATTR is more heavily impacted than that of AL. However, larger sample sizes are needed to determine if the differences are chance findings due to a large number of immune markers.