Tuberculosis is a curable and preventable contagious disease affecting around a quarter of the world’s population with a major cause of human mortality caused by the bacillus Mycobacterium tuberculosis (M tb) that mainly affects the lungs and also other parts of the body. About 10.6 million people developed TB, 1.3 million people died from TB and the net reduction during 2015–2022 is 8.7 %, far from the TB end strategy [1]. Persons with active pulmonary TB (APTB) are contagious and spread TB to others, whereas persons with latent TB infection (LTBI) are not contagious [2]. Usually, LTBI people do not show any symptoms, but they react positively to a tuberculin skin test (TST) or IGRA test [3]. According to estimates worldwide, 33 % of people have latent TB infections (LTBI), and about ∼ 5–10 % of them who do not receive treatment for LTBI will develop active TB in their lifetime [4]. The close contacts and household members of active TB patients who are immunocompromised with malnourishment, secondary immune disorders, or a habit of tobacco, smoke, and alcohol have a higher risk of developing active TB within 1–2 years of their exposure to M tb [5]. The existing diagnosis and treatments were insufficient to control and meet the target of TB elimination by 2050 [6]. Therefore, an early diagnosis of active disease from latent infection would be highly beneficial for efficient treatment in preventing TB disease progression [7].

TB pathogenesis is an interaction between the host immune system and M tb survival mechanisms [8]. The initial host-pathogen interaction begins with the recognition of the mycobacterial antigens by phagocytic receptors, which leads to the production of chemokines and cytokines for recruiting and activating inflammatory cells [9]. Following this initial interaction, M tb moves to lymph nodes and initiates antigen-specific T cells, which further differentiate into cytokine-secreting cells that express chemokine receptors to export them from lymph nodes to the inflammation site. These T cells then release cytokines and chemokines to activate and migrate immune cells to the inflamed sites, resulting in the formation of granuloma that controls the infection by preventing the growth and spread of M tb which leads to latency [7], [8]. So, it is understood that these cytokines and chemokines play a major role in communicating with the immune cells, which is important for both migration and giving specific instructions to the host immunity for controlling TB [7]. On the other hand, M tb is able to express certain proteins that promote inflammatory responses that are regulated by the host immune response to avoid tissue damage. When the host immune system fails to regulate these inflammatory responses, M tb multiplies rapidly, which cannot be controlled immediately by the host immunity towards the disease progression [7]. The secretory proteins of M tb are capable of manipulating the host immune response by interacting with human T cells and dendritic cells at early stages of infection during M tb growth and are involved in the establishment and persistence of M tb within macrophages. The M tb proteins of the pathogen and MCP-1 of the host play a critical role in tuberculosis development. Though the M tb proteins induce chemokines in the host towards the inflammatory response, their relationship in the host immune mechanism is not clear.

The major secretory proteins of M tb are Antigen 85A and ESAT6 (6-kDa early secreted antigenic target), which induce strong cellular and humoral immune responses upon infecting the host. The Ag85 complex proteins (Ag85A, B, and C) help in the active replication of M tb in TB pathogenesis [10], [11]. Ag85A and Ag85B proteins are involved in the stimulation of strong T-cell proliferation and the production of IFN-γ in latent infections. Upon disruption of the Ag85 complex, Ag85A plays a major role in the early stages of infection during M tb growth and is involved in the establishment and maintenance of persistence within macrophages [12], [13]. ESAT-6 is a key virulent factor and potent T-cell antigen secreted through ESX-1 (ESAT-6 secretion system-1) of M tb, which acts as a pore-forming toxin for the virulence of M tb. It mediates cytosolic translocation of M tb within the host macrophages by rupturing phagosomal membranes and involves in the virulence and pathogenesis of tuberculosis [14]. ESAT6 plays a role in host macrophage differentiation and activation, inducing granuloma formation and bringing down the immune response to maintain its persistence [15]. Ag85A and ESAT6 expressed in growing bacilli are associated with different growth phases and correlated with bacterial load in active TB patients, followed by LTBI individuals [16].

Cytokines are an important proteins in the regulation of immune responses to pathological and physiological conditions [17]. Macrophages infected with M tb secrete pro-inflammatory cytokines, TNF-α (tumor necrosis factor-alpha) to recruit CD4 + and CD8 + T cells to the infection site, and IFN-γ (interferon-gamma) to activate macrophages for killing the pathogen [18]. The anti-inflammatory cytokines IL-10 (interleukin-10) and TGF-β (transforming growth factor-beta) produced towards M tb, act as immunosuppressive cytokines by down-regulating the immune response and minimizing tissue injury by inhibiting the inflammatory response [19]. These IL-10 and TGF-β cytokines have been involved in decreased T cell function during TB, which would be involved in shifting the latent state to active tuberculosis [20]. The pro-inflammatory cytokines are associated with protection against TB, whereas anti-inflammatory cytokines are associated with susceptibility to TB [21].

Chemokines are the chemotactic cytokines that belong to a large family of proteins, acts as chemoattractants for neutrophils, lymphocytes, and monocytes recruitment from the blood into tissues in response to inflammation. Among all the chemokines, MCP-1 (monocyte chemoattractant protein-1) plays an important role in TB pathogenesis, which is associated with granuloma formation and TB severity by aggregating the immune cells to the inflammation site [22], [23]. Studies reported that M tb antigens enhance the production of MCP-1, but their mechanism in macrophage activation with tuberculosis infection is not clear.

Microbial pathogens have been shown to induce various cytokines, their receptors, and chemokines, which are involved in the suppression of the host immune response and inflammatory defenses [24]. To enhance the host’s immunity against infection, recombinant cytokines are designed to stimulate specific immune cells by overcoming immunosuppressive signals mediated by the pathogen. However, recombinant cytokines are used for experimental and therapeutic purposes to treat several diseases [25], but their mechanism is unclear. Hence, in the present study recombinant cytokines were used as in-vitro stimulants to determine their effect on the secretion and expression of immunoregulatory proteins. Many studies reported the role of different cytokines and chemokines in tuberculosis in distinguishing latent and active TB, but their synergetic role in host immune mechanism is not clear yet. Therefore, there is a need to understand the mechanism of interaction of M tb proteins, cytokines, and chemokines, which might help in distinguishing active and latent TB. Hence, in the present study we have hypothesized to know the in vitro stimulatory effect of M tb antigens, recombinant cytokines on the secretion and expression of chemokine MCP-1 in APTB patients, their contacts and healthy controls.