A 20-year medical follow-up report on the changes in the immune systems of three patients with moderate or severe bone marrow form of acute radiation sickness in the "4.26" ⁶⁰Co radiation accident in Henan province

Objective To observe the long-term effects on the immune systems of three patients with moderate or severe bone marrow form of acute radiation sickness in the "4.26" ⁶⁰Co radiation accident in Henan province and summarize the characteristics of long-term changes in the immune system after acute radiation injury.

Methods Two patients ("Tian" and "Wang"; aged 37 and 8 years, respectively; both were males) with moderate bone marrow form of acute radiation sickness and one patient ("Mei"; female; 38 years old) with severe bone marrow form of acute radiation sickness in the "4.26" ⁶⁰Co radiation accident in 1999 were followed up. The levels of serum immunoglobulin (Ig) A, IgG, IgM, and complement C3 in the patients' peripheral blood were detected through immune turbidimetry and used in evaluating humoral immunity. T lymphocyte subsets (including the percentages of CD3⁺, CD3⁺CD4⁺, and CD3⁺CD8⁺ T-cells and the ratio of CD3⁺CD4⁺ T-cells to CD3⁺CD8⁺ T-cells) were analyzed through flow cytometry for the evaluation of cellular immunity.

Results The follow-up time was up to September 4, 2019, with a total of 11 times. Humoral immunity results showed that the complement C3 level of "Mei" decreased in half a year and in the second year, and her IgG level increased in the 5th, 11th, 13th, and 20th years. The IgM and IgG levels of "Tian" decreased in the third year and increased in the fifth year, respectively. As for "Wang", the complement C3 level increased in the first and fifth years after irradiation. The abnormal frequency and duration of Ig showed as "Mei">"Tian"="Wang". Cellular immunity results showed that the percentage of CD3⁺ and CD3⁺CD4⁺ T-cells and the ratio of CD3⁺CD4⁺ T-cells to CD3⁺CD8⁺ T-cells of "Mei" decreased significantly half a year after irradiation, and the percentages of her CD3⁺, CD3⁺CD4⁺, and CD3⁺CD8⁺ T-cells decreased in the seventh and 11th years, and the percentages of her CD3⁺ and CD3⁺CD4⁺ T-cells decreased in the 15th year. The percentages of CD3⁺CD4⁺ T-cells of "Tian" increased 5 and 11 years after irradiation, and the percentages of his CD3⁺ and CD3⁺CD8⁺ T-cells decreased in the seventh year. The percentages of CD3⁺, CD3⁺CD4⁺, and CD3⁺CD8⁺ T-cells of "Wang" decreased 7 years after irradiation. The abnormal frequency and duration of T lymphocyte subsets showed as "Mei">"Tian">"Wang".

Conclusions The acute radiation-induced damage to the immune system is long term, dose-dependent, and reversible. For individuals, the damage to immune system is positively correlated with radiation dose, and age and gender are the possible influencing factors.