Activated Lymphocytes in Malaria and Typhoid Fever
Yes, activated lymphocytes are present in both malaria and typhoid fever, though the patterns differ significantly between these two infections.
Lymphocyte Activation in Typhoid Fever
Typhoid fever demonstrates clear evidence of lymphocyte activation with characteristic alterations in T-cell populations. Research shows that patients with typhoid fever have increased lymphocyte adenosine deaminase (L-ADA) activity, which serves as a marker of immune response and lymphocyte activation 1. This enzymatic increase is prolonged and persists despite treatment, directly correlating with the immune response 1.
T-Cell Subset Alterations
The ratio of T lymphocyte subpopulations becomes grossly imbalanced in typhoid patients, with significant changes in T cells bearing receptors for IgM (Tμ) and IgG (Tγ) 2.
Complicated cases of typhoid fever show more severe alterations in T lymphocyte numbers and subpopulations compared to uncomplicated cases 2.
Cell-mediated immune response (CMIR) remains intact in uncomplicated typhoid cases but becomes depressed in complicated cases, suggesting that the imbalance within T lymphocyte subsets is responsible for this immunosuppression 2.
The presence of activated lymphocytes and intact CMIR may be more critical for recovery in typhoid fever than specific antibody production 2.
Lymphocyte Activation in Malaria
While the provided guidelines focus primarily on clinical and laboratory diagnostic features of malaria rather than specific cellular immune responses, malaria is well-established to trigger significant lymphocyte activation as part of the host immune response. The clinical guidelines emphasize that:
Lymphopenia is common in malaria, particularly in severe cases and with certain viral co-infections like dengue and HIV 3.
Thrombocytopenia (<150,000/μL) is the most frequent laboratory finding in malaria, occurring in 70-79% of patients regardless of Plasmodium species 3.
Clinical Differentiation
Key Laboratory Findings
In malaria: Thrombocytopenia (positive likelihood ratio 5.6-11.0), hyperbilirubinemia (positive likelihood ratio 5.3-7.3), and lymphopenia are characteristic 3.
In typhoid fever: Lymphopenia is common, with blood cultures showing 80% sensitivity in the first week 3.
Diagnostic Pitfalls
A critical caveat is that co-infection with malaria and typhoid can occur, particularly in endemic regions like Malaysia, India, and Cameroon 4, 5. However, the number of cases diagnosed as concurrent malaria-typhoid infection is frequently overestimated when relying solely on serological tests 5, 6. One study found that only 17% of patients had true concurrent infection based on bacteriological diagnosis, compared to 47.9% based on Widal test alone 5.
Practical Approach
Always exclude malaria first in any febrile patient returning from tropical areas, as it is the most important potentially fatal cause 7, 8.
Obtain blood cultures before initiating antibiotics for suspected typhoid fever, as they are the gold standard for diagnosis 7.
Do not rely solely on Widal testing or malaria antibody card tests for diagnosing co-infection, as these have high false-positive rates 5, 6.
Confirmed co-infection rates are much lower (1.6%) than suggested by serological testing alone 6.