Antibody titer after vaccination

Assembly and secretion of antibodies

Before antibodies enter the blood and form a protective titer, they must be synthesized inside a plasma cell. There are two main pathways for the assembly of a "mature" immunoglobulin (Ig) molecule:

• First pathway (typical for IgG): First, heavy (H) chains undergo dimerization. Then, two light (L) chains sequentially attach to the resulting H-dimer. Scheme: H + H → H2, then H2 + L → H2L, and finally H2L + L → H2L2.
• Second pathway (typical for IgM): Initially, a dimer is formed from one heavy and one light chain (H + L → HL). After that, two such complexes combine into a full-length molecule (HL + HL → H2L2).

The formed soluble form of Ig is not capable of embedding into the cell membrane. Its intracellular route is strictly defined: endoplasmic reticulum → Golgi apparatus (where processing and glycosylation are carried out) → secretory vesicles → release from the cell.

Kinetics of antibody production

During the primary immune response to an administered vaccine, the dynamics of serum antibodies mimic the activity of producer cells, but with a slight time delay.

• IgM antibodies: Secreted first. It has been proven in mouse models that the growth in the number of producer cells begins on day 2, peaks in the spleen on day 4, and drops sharply after day 5. In blood serum, the maximum IgM titer is detected on days 5–6.
• IgG antibodies: Cells synthesizing this class appear in the spleen starting from day 4, and their peak occurs on days 8–10. The depletion of these cells proceeds much more slowly. The serum IgG titer reaches its maximum on days 10–12. High levels persist until days 20–25, after which a slow decline begins, lasting 2–3 months.
• IgA and IgE antibodies: Their kinetics in blood serum generally repeat the graph of IgG production.

Distribution of immunoglobulins in the body

After leaving the cells, antibodies are distributed unevenly across various body compartments:

• Blood serum: Here, IgG class antibodies (in particular, the IgG1 subclass) are absolute dominants. This predominance becomes especially pronounced during a secondary immune response.
• Mucous membranes: In barrier tissues, the synthesis and secretion of IgA absolutely prevail. It accounts for up to 90% of all immunoglobulins secreted here.
• Secondary lymphoid organs (outside barrier tissues): The proportions of synthesized antibodies are distributed differently. IgG accounts for 55–66%, IgA for 11–30%, and IgM for 15–23%.

Life span of plasma cells

The duration of the protective antibody titer persistence after vaccination directly depends on the lifespan of plasma cells.

1. Short-lived (5–7 days): These are cells induced in vitro, isolated from the body after in vivo induction, as well as those formed under suboptimal conditions (for example, if they did not pass through germinal centers).
2. Medium-lived (4–7 weeks): Plasma cells that localize in the spleen and lymph nodes.
3. Long-lived: The lifespan of cells increases significantly upon their migration to the bone marrow. Vaccination can induce a lifelong level of antibodies. Science has recorded a case where a plasma cell secreting antiviral antibodies lived for 75 years.

Practice: vaccine prophylaxis and monitoring

Due to individual differences in the immune system, selecting a personalized vaccine dose is extremely difficult. Therefore, the mass immunization strategy relies on doses and administration routes that ensure a response in the majority of people. The main goal is to reach the epidemiological threshold at which immunity is present in 95% of the population.

Special monitoring is required before prescribing immunosuppressive therapy. The physician must take an anamnesis regarding past vaccine-preventable infections (measles, rubella, chickenpox, mumps) and evaluate the strength of immunity to the pathogens via laboratory tests.

For example, patients with Crohn's disease (CD) remain at high risk for an inadequate response to standard vaccines. They are recommended selective titer control no earlier than 1 month after the course. If blood testing for antibodies to hepatitis B surface antigen (anti-HBs) shows no protective titer, the patient is given a booster dose.

Class and exam questions

What else to study on this topic

• Processing and glycosylation of immunoglobulins in the Golgi apparatus
• Mechanisms of short-lived plasmacyte formation outside germinal centers
• Features of the secondary immune response and dominance of the IgG1 subclass
• Causes of inadequate immune response to vaccines in Crohn's disease
• Significance of the 95% epidemiological threshold for preventing outbreaks of infections

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.