African-Americans and Hispanics with relapsing-remitting multiple sclerosis (RRMS) have higher blood levels of plasmablasts, a type of inflammatory immune cell that produces antibodies, than do Caucasians with this disease, a study found.
The study “Black African and Latino/a identity correlates with increased plasmablasts in MS” was published in the journal Neurology, Neuroimmunology and Neuroinflammation.
Previous research supports MS progression being more severe in African-Americans and Hispanics and Latino-Americans compared to Caucasians. Among these two ethnic groups, brain atrophy (shrinkage) and retina degeneration occurs faster, and inflammation of the central nervous system (brain and spinal cord) is more evident.
Still, few studies fairly represent patients by ethnic or racial background despite evident differences in disease course. According to the researchers, only 2.7% of all MS patients enrolled in seven Phase 3 clinical trials testing potential treatments between 2006 and 2017 were African-American.
Disease mechanisms underlying racial and ethnic differences in disease progression are also unknown.
Immune cells like plasmablasts and plasma cells (antibody-producing cells that derive from immune B-cells) have been linked to the inflammatory and neurodegenerative processes that occur in MS.
Previous research has also shown that black patients have higher levels than white patients of a type of antibody called IgG in their cerebrospinal fluid (CSF). High IgG levels are associated with greater atrophy of the brain’s gray matter.
To evaluate whether the levels of antibody-secreting cells could differ between MS patients of different ethnic groups, researchers at Weill Cornell Medicine in New York looked at the frequency of immune cells in blood samples from patients.
They analyzed samples from 74 people with RRMS — 27 African-Americans or Hispanics/Latinos, and 27 Caucasians — all treated with Tysabri (natalizumab), samples from 20 patients not on any disease-modifying therapy (12 black or Hispanic/Latino; eight white), and samples from 24 age- and ethnicity-matched healthy people (11 black or Hispanic/Latino; 13 white).
Tysabri was chosen because it does not destroy antibody-producing cells, which the team aimed to study.
Results showed that patients of African or Hispanic origin generally had a higher frequency of antibody-secreting cells compared to those of Caucasian ancestry. In particular, most of these cells were positive for a surface protein called CD86, a marker used to identify plasmablasts, and other subsets associated with a poorer prognosis and a more active MS disease course.
These differences in antibody-secreting cell levels by ethnicity were only found among MS patients; they were not evident among healthy controls.
Patients of African or Hispanic origin also showed signs of greater disease activity, taking a mean of 4.29 seconds to complete the timed 25-foot walk test compared to 3.70 seconds among Caucasian patients.
These findings showed that MS patients of African-American or Hispanic ancestry have higher levels of antibody-secreting cells like plasmablasts, and suggest this may be the cause of the more severe disease course seen in these people.
“This dysregulation may contribute to the disease disparity experienced by patient populations of Black African or Latin American ethno-ancestry,” the researchers wrote.
The team advised that “further study is necessary to confirm the results, and more fully understand their implications for improving the management of MS in these populations.”