How does the human immune system fight infections?

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1. 1

   Effects of Viruses on Innate and Adaptive Immunity: Mechanisms, Challenges, and Prevention

   Journal of Wasit for Science and Medicine (AL-Ukaily & Al-Tamimi)Published Feb 10, 2026Checked Oct 11, 2026

   “Viruses pose a serious threat to human health by hijacking host cellular machinery and altering immune responses. Understanding virus–immune system interactions is crucial for controlling viral diseases. This study focuses on the roles of innate and adaptive immunity in antiviral defense. Innate immunity provides the first barrier through pattern recognition receptors (PRRs) and type I interferon signaling, whereas adaptive immunity mediates antigen-specific responses and immune memory. However, many viruses evade immunity through mechanisms such as interferon inhibition, antigenic variation, latency, and T-cell exhaustion, especially in chronic infections like HIV, HBV, and HCV. These strategies promote immune dysfunction and viral persistence. Recent therapeutic advances, including mRNA vaccines, monoclonal antibodies, immune checkpoint inhibitors, and nanotechnology-based delivery systems, offer promising approaches to enhance antiviral immunity and limit viral replication.”

2. 2

   The Human Immune Response to Respiratory Syncytial Virus Infection

   Clinical Microbiology Reviews (Russell et al.)Published Feb 9, 2017Checked Oct 11, 2026

   “There is an initial strong neutrophil response to RSV infection in humans, which is positively correlated with disease severity and mediated by interleukin-8 (IL-8). Dendritic cells migrate to the lungs as the primary antigen-presenting cell. An initial systemic T-cell lymphopenia is followed by a pulmonary CD8+T-cell response, mediating viral clearance. Humoral immunity to reinfection is incomplete, but RSV IgG and IgA are protective. B-cell-stimulating factors derived from airway epithelium play a major role in protective antibody generation. Gamma interferon (IFN-γ) has a strongly protective role, and a Th2-biased response may be deleterious. Other cytokines (particularly IL-17A), chemokines (particularly CCL-5 and CCL-3), and local innate immune factors (including cathelicidins and IFN-λ) contribute to pathogenesis. In summary, neutrophilic inflammation is incriminated as a harmful response, whereas CD8+T cells and IFN-γ have protective roles. These may represent important therapeutic targets to modulate the immunopathogenesis of RSV infection.”

3. 3

   Cellular Immune Response to High-Risk Human Papillomavirus Infection: A Systematic Review

   Critical Reviews in Immunology (Fonseca et al.)Published Jan 1, 2025Checked Oct 11, 2026

   “After the systematic review steps, the final number of included studies was 22. Cervical lesions were distributed according to the severity of lesions in HSIL, low-grade squamous intraepithelial lesions (LSIL), and negative for intraepithelial lesions or malignancy (NILM). The cellular phenotypes presented in these publications were T lymphocytes (LT), regulatory T lymphocytes (Tregs), macrophages (MØ), natural killer cells (NK), natural killer T cells (NKT), Langerhans cells (LC), and dendritic cells (DC). Among the observed associations with cervical lesions and HR-HPV, we highlight the DC/LC and MØ being 36.4% of the cell types, followed by Tregs (31.8%) and LT CD4 / CD8 with 27.3%. The increased findings in innate and adaptive immunological response may imply both are acting together, with the innate response cells and Tregs being the most prominent. Since these cells have great importance in the maintenance and balance of the immunological system, the present study highlights the essential role of MØ and Treg cells in the process of cervical lesion severity associated with HPV, suggesting that they may be focused as prognostic markers and immunotherapeutic targets.”

4. 4

   The host transcriptional response to real-world cryptococcosis in the setting of advanced HIV disease defines dysregulated immune responses that underlie increased vulnerability to infection.

   The Journal of infectious diseases (Sim et al.)Published Oct 1, 2026Checked Oct 11, 2026

   “Penalized logistic regression was used to identify gene expression signatures capable of identifying Cryptococcus disease.ResultsOut of 118 participants, 13 (11%) had cryptococcal disease and 41 (34.7%) were persons living with HIV (PLWH). Genes upregulated in response to cryptococcosis compared to non-acutely-infected community controls reflected complement activation, neutrophil activation, type I interferon signaling, and myeloid dendritic cell differentiation. When compared to combined bacterial or viral illnesses, cryptococcal disease demonstrated hyperactivation of both innate and humoral immune pathways. A series of classifiers were developed that distinguished between cryptococcal and combined bacterial or viral diseases with an AUC of 0.946.ConclusionOverall, the host response to cryptococcosis in individuals with advanced HIV as manifested in transcriptional profiles informs our understanding of the pathophysiology of and susceptibility to cryptococcal infection and may support development of novel diagnostic and therapeutic approaches.”

5. 5

   The impact of obesity on the immune response to infection

   Proceedings of The Nutrition Society (Milner & Beck)Published Mar 14, 2012Checked Oct 11, 2026

   “However, relatively little is known of how the immune system and host defence are influenced by the pro-inflammatory and excess energy milieu of the obese. Epidemiological data suggest obese human subjects are at greater risk for nosocomial infections, especially following surgery. Additionally, the significance of altered immunity in obese human subjects is emphasised by recent studies reporting obesity to be an independent risk factor for increased morbidity and mortality following infection with the 2009 pandemic influenza A (H1N1) virus. Rodent models offer important insight into how metabolic abnormalities associated with excess body weight can impair immunity. However, more research is necessary to understand the specific aspects of immunity that are impaired and what factors are contributing to reduced immunocompetence in the obese. Additionally, special consideration of how infection in this at-risk population is managed is required, given that this population may not respond optimally to antimicrobial drugs and vaccination. Obesity impacts millions globally, and greater understanding of its associated physiological disturbances is a key public health concern.”