According to a 2022 review addressing use of immunotherapies in neuroimmunologic diseases, vaccination should ideally be completed before immunotherapy when feasible, and antibody titer monitoring may be considered when responses may be diminished. In cases of plasma exchange, the authors note that vaccine responses have not been systematically studied during exchange sessions. Vaccines administered during plasma exchange or 2 to 4 weeks before sessions may have compromised responses, as vaccine antigens could be removed during the exchange; similarly, passive immunization with immunoglobulin may be ineffective during this period because circulating antibodies are directly removed. Importantly, plasma exchange does not eliminate cellular immune mechanisms, and after completion of treatment, cytokine and immunoglobulin production are expected to normalize within days. Based on these considerations, the authors suggest that vaccination generally does not need to be delayed for more than 1 to 2 weeks after completion of plasma exchange, while acknowledging that studies directly defining vaccine immunogenicity and optimal timing around plasma exchange are lacking. [1]
Mechanistically, membrane therapeutic plasma exchange (TPE) separates plasma from other cellular components of blood through a highly permeable membrane; the removed plasma is discarded, and an equal volume of replacement fluid, typically albumin or fresh frozen plasma, is infused. The procedure is designed to remove large-molecular-weight substances such as immunoglobulins, proteins, immune complexes, and lipoproteins that are not effectively removed by conventional dialysis or hemofiltration. Modern plasma-separation membranes have very high sieving coefficients for plasma proteins, including a sieving coefficient of approximately 1 for immunoglobulin G (IgG). Membrane TPE has been shown to remove immunoglobulins with efficacy similar to centrifugal TPE. [2]
The extent of removal depends on the volume of plasma exchanged as well as the intravascular distribution and half-life of the target molecule. IgM is approximately 78% intravascular with a half-life of 5 days, whereas IgG is less than 45% intravascular with a half-life of 21 days. After each treatment, concentrations can rise over the following 24 to 48 hours because of new generation and equilibration between the extravascular and intravascular compartments. An exchange of 1 estimated plasma volume lowers pretreatment immunoglobulin concentrations by approximately 63%, while an exchange of 1.43 estimated plasma volumes lowers concentrations by approximately 75%; exchanging more than approximately 1.5 plasma volumes during a single session provides little additional removal. Ideally, medications such as IgG and therapeutic antibodies should be scheduled after plasma exchange to avoid their removal. [2]