Why is immunoglobulin administered after a tick bite? - briefly
Immunoglobulin is administered after a tick bite to confer immediate passive immunity against potential tick‑borne pathogens, especially when the threat of severe infection such as Lyme disease or tick‑borne encephalitis is high. It neutralizes toxins and supports pathogen clearance while the recipient’s own antibody response matures.
Why is immunoglobulin administered after a tick bite? - in detail
Passive immunization with specific antitick‑borne encephalitis (TBE) immunoglobulin is employed when a person is exposed to a tick in a region where TBE virus circulates and lacks protective vaccine‑induced antibodies. The preparation supplies high‑titer neutralizing antibodies that bind viral particles at the bite site, preventing replication and spread to the central nervous system. Because active immunity requires at least a week to develop, the immediate protection offered by immunoglobulin is essential for individuals at high risk of severe disease.
Indications for administration include:
- No prior TBE vaccination or incomplete vaccination schedule.
- Immunocompromised status that impairs vaccine response.
- Exposure to a tick in a highly endemic area during peak transmission season.
- Presentation within 72 hours of the bite; efficacy declines sharply after this window.
The recommended regimen consists of a single intramuscular dose of 0.1 mL/kg body weight of human TBE‑specific immunoglobulin, injected into the deltoid muscle. The dose delivers sufficient antibody concentration to achieve passive protection until active immunity can be established, if subsequent vaccination is planned.
Mechanistically, the infused IgG molecules bind epitopes on the viral envelope glycoprotein, blocking attachment to host cell receptors and facilitating opsonization. This neutralization halts the early phase of infection, reducing viral load and the likelihood of neuroinvasion. Passive antibodies also modulate the immune response by engaging Fc receptors on macrophages, enhancing clearance of infected cells.
Clinical data show that timely immunoglobulin therapy reduces the incidence of symptomatic TBE by up to 90 % in unvaccinated individuals. The benefit is most pronounced in elderly patients and those with chronic illnesses, who are otherwise prone to severe neurological sequelae.
In summary, the use of TBE‑specific immunoglobulin after a tick bite delivers rapid, virus‑neutralizing immunity, bridges the gap before active vaccine‑induced protection can develop, and is reserved for high‑risk, unvaccinated, or immunologically compromised patients who seek immediate prophylaxis.