Role of DNA-binding antibodies in kidney pathology associated with murine malaria infections

Autoantibodies during infectious diseases: Lessons from malaria applied to COVID-19 and other infections

Autoimmunity is a common phenomenon reported in many globally relevant infections, including malaria and COVID-19. These and other highly inflammatory diseases have been associated with the presence of autoantibodies. The role that these autoantibodies play during infection has been an emerging topic of interest. The vast numbers of studies reporting a range of autoantibodies targeting cellular antigens, such as dsDNA and lipids, but also immune molecules, such as cytokines, during malaria, COVID-19 and other infections, underscore the importance that autoimmunity can play during infection. During both malaria and COVID-19, the presence of autoantibodies has been correlated with associated pathologies such as malarial anemia and severe COVID-19. Additionally, high levels of Atypical/Autoimmune B cells (ABCs and atypical B cells) have been observed in both diseases. The growing literature of autoimmune B cells, age-associated B cells and atypical B cells in Systemic Lupus erythematosus (SLE) and other autoimmune disorders has identified recent mechanistic and cellular targets that could explain the development of autoantibodies during infection. These new findings establish a link between immune responses during infection and autoimmune disorders, highlighting shared mechanistic insights. In this review, we focus on the recent evidence of autoantibody generation during malaria and other infectious diseases and their potential pathological role, exploring possible mechanisms that may explain the development of autoimmunity during infections.

Autoantibodies and Malaria: Where We Stand? Insights Into Pathogenesis and Protection

Autoantibodies are frequently reported in patients with malaria, but whether they contribute to protection or to pathology is an issue of debate. A large body of evidence indicates that antibodies against host-self components are associated to malaria clinical outcomes such as cerebral malaria, renal dysfunction and anemia. Nonetheless, self-reactive immunoglobulins induced during an infection can also mediate protection. In light of these controversies, we summarize here the latest findings in our understanding of autoimmune responses in malaria, focusing on Plasmodium falciparum and Plasmodium vivax. We review the main targets of self-antibody responses in malaria as well as the current, but still limited, knowledge of their role in disease pathogenesis or protection.

Autoimmune Anemia in Malaria

Severe anemia is a major cause of death by malaria. The loss of uninfected erythrocytes is an important contributor to malarial anemia; however, the mechanisms underlying this pathology are not well understood. Malaria-induced anemia is related to autoimmune antibodies against the membrane lipid phosphatidylserine (PS). In mice, these antibodies induce the clearance of uninfected erythrocytes after binding to PS exposed in their membrane. In human malaria patients there is a strong correlation between anemia and anti-PS antibodies. During malaria, anti-PS antibodies are produced by atypical B cells, whose levels correlate with the development of anemia in patients. Autoimmune responses, which are documented frequently in different infections, contribute to the pathogenesis of malaria by inducing the clearance of uninfected erythrocytes.

Divergent Roles of Antiself Antibodies during Infection

Antiself antibodies are most commonly associated with autoimmune disorders, but a large body of evidence indicates that they are also present in numerous infectious diseases. These autoimmune antibodies appear transiently during infection with a number of viruses, bacteria, and parasites and in some cases have been associated with the development of autoimmune disorders that develop after infection has been cleared. Traditionally these infection-associated autoantibodies are considered an erroneous byproduct of a legitimate immune response, but their possible role in the clearance of microbes and infected cells or inhibition of host-cell invasion suggests that they may be present because of their beneficial protective role against various infections.

Serologic features of cohorts with variable genetic risk for systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease with genetic, hormonal, and environmental influences. In Western Europe and North America, individuals of West African descent have a 3-4 fold greater incidence of SLE than Caucasians. Paradoxically, West Africans in sub-Saharan Africa appear to have a low incidence of SLE, and some studies suggest a milder disease with less nephritis. In this study, we analyzed sera from African American female SLE patients and four other cohorts, one with SLE and others with varying degrees of risk for SLE in order to identify serologic factors that might correlate with risk of or protection against SLE.

METHODS

Our cohorts included West African women with previous malaria infection assumed to be protected from development of SLE, clinically unaffected sisters of SLE patients with high risk of developing SLE, healthy African American women with intermediate risk, healthy Caucasian women with low risk of developing SLE, and women with a diagnosis of SLE. We developed a lupus risk index (LRI) based on titers of IgM and IgG anti-double stranded DNA antibodies and levels of C1q.

RESULTS

The risk index was highest in SLE patients; second highest in unaffected sisters of SLE patients; third highest in healthy African-American women and lowest in healthy Caucasian women and malaria-exposed West African women.

CONCLUSION

This risk index may be useful in early interventions to prevent SLE. In addition, it suggests new therapeutic approaches for the treatment of SLE.

Chronic spontaneous urticaria and internal parasites--a systematic review

Chronic spontaneous urticaria (CSU) is defined as persistent wheals, angioedema, or both lasting for >6 weeks due to known or unknown causes. Some epidemiological studies and case reports suggest that internal parasite infections (PI) can cause CSU. Here, we provide a systematic overview of published findings on the prevalence and relevance of PI in CSU and we discuss possible pathomechanisms. The prevalence of PI in CSU was investigated by 39 independent studies and comorbidity reportedly ranged from 0 to 75.4% (two-thirds of these studies reported infection rates of 10% or less). The prevalence of PI in adult and pediatric CSU patients ranged from 0% to 75.4% and from 0% to 37.8%, respectively. CSU patients were more often diagnosed with protozoa and had a significantly higher risk of toxocariasis seropositivity and Anisakis simplex sensitization when compared to healthy controls. Patients with chronic urticaria more frequently had seropositivity of fasciolosis, Anisakis simplex sensitization, and the presence of Blastocystis hominis allele 34 (ST3) as compared with control subjects. In 21 studies, efficacy of treatment with antiparasitic drugs ranged from 0 to 100% (35.7% of 269 CSU patients benefitted). In 9 (42.8%) of 21 studies, more than 50% of efficacy was observed. The reported rate of urticaria comorbidity in PI patients in 18 independent studies is 1-66.7%. Urticaria including CSU might be a quite common symptom of strongyloidiasis and blastocystosis. Pathogenic mechanisms in CSU due to PI may include specific IgE, Th2 cytokine skewing, eosinophils, activation of the complement, and the coagulation systems.

Potential immune mechanisms associated with anemia in Plasmodium vivax malaria: a puzzling question

The pathogenesis of malaria is complex, generating a broad spectrum of clinical manifestations. One of the major complications and concerns in malaria is anemia, which is responsible for considerable morbidity in the developing world, especially in children and pregnant women. Despite its enormous health importance, the immunological mechanisms involved in malaria-induced anemia remain incompletely understood. Plasmodium vivax, one of the causative agents of human malaria, is known to induce a strong inflammatory response with a robust production of immune effectors, including cytokines and antibodies. Therefore, it is possible that the extent of the immune response not only may facilitate the parasite killing but also may provoke severe illness, including anemia. In this review, we consider potential immune effectors and their possible involvement in generating this clinical outcome during P. vivax infections.

Epidemiology, pathophysiology, management and outcome of renal dysfunction associated with plasmodia infection

Malaria remains a serious health problem in many parts of the world. It causes high morbidity and claims many lives in developing countries each year. Humans are generally infected by four species of malaria parasites. However, malaria infection caused by Plasmodium malariae or P. falciparum is recognized as an important cause of acute renal failure (ARF) and other renal-related disorders (nephropathy) in infected patients. The increasing incidence of malarial ARF (MARF) and the emergence of clinical malarial infection after renal transplantation represent a serious challenge. Additionally, the impact of immunosuppressive therapies on malarial infection is intricate, complex, and not yet well defined. Pathogenesis of MARF is most likely to be due to immune complex-mediated glomerulonephritis caused by immune-complex deposition and endothelial damage, which may lead to fatal forms of quartan malarial nephropathies. Effects of mechanical, immunologic, cytokine, humoral, acute phase response, and hemodynamics factors in inducing malarial nephropathy have also been postulated. Development of preventive strategies aimed at combating MARF and other renal disorders associated with malaria infection requires (1) prevention of malarial infection, (2) early diagnosis, and (3) early referral to well-equipped centers to provide renal replacement therapy, if necessary, along with antimalarial therapy and support. These measures could significantly reduce mortality and enhance recovery of renal function.

Malaria-induced renal damage: facts and myths

Malaria infections repeatedly have been reported to induce nephrotic syndrome and acute renal failure. Questions have been raised whether the association of a nephrotic syndrome with quartan malaria was only coincidental, and whether the acute renal failure was a specific or unspecific consequence of Plasmodium falciparum infection. This review attempts to answer questions about "chronic quartan malaria nephropathy" and "acute falciparum malaria nephropathy". The literature review was performed on all publications on kidney involvement in human and experimental malarial infections accessible in PubMed or available at the library of the London School of Hygiene and Tropical Medicine. The association of a nephrotic syndrome with quartan malaria was mostly described before 1975 in children and rarely in adult patients living in areas endemic for Plasmodium malariae. The pooled data on malaria-induced acute renal failure included children and adults acquiring falciparum malaria in endemic areas either as natives or as travellers from non-tropical countries. Non-immunes (not living in endemic areas) had a higher risk of developing acute renal failure than semi-immunes (living in endemic areas). Children with cerebral malaria had a higher rate and more severe course of acute renal failure than children with mild malaria. Today, there is no evidence of a dominant role of steroid-resistant and chronic "malarial glomerulopathies" in children with a nephrotic syndrome in Africa. Acute renal failure was a frequent and serious complication of falciparum malaria in non-immune adults. However, recently it has been reported more often in semi-immune African children with associated morbidity and mortality.

Human leukocyte antigen (HLA) associations, antibody titers and circulating immune complexes in patients with cystic echinococcosis

Cystic echinococcosis (CE), caused by the parasite Echinococcus granulosus, is a prominent disease in Lebanon. The objectives of this study were to determine HLA allele-CE association in patients, and relate its presence to high anti-Echinococcus antibody titers and the presence of circulating immune complexes (CIC). Thirty patients and 20 controls were included. HLA profiles were determined by DNA-SSP typing. Relative risk and P-values were determined for each allele using Statcalc (EpiInfo, Version 6). Linkage disequilibrium was determined for associated alleles using SPSS 12.0 for Windows. Antibody titers were determined by indirect hemagglutination (IHA) and CIC by polyethylene glycol (PEG) precipitation. HLA-B*14 and HLA-DRB1*01 appeared to associate with protection against CE (P1 = P2 = 0.007 and P1 = P2 = 0.0007, respectively). However, it appeared that linkage disequilibrium did not exist between these 2 alleles (P = 0.250). HLA-B*35 was found to associate with susceptibility to disease (RR = 1.70, P = 0.02). Twenty five patients had anti-Echinococcus antibodies and 9 patients had CICs. However, there did not appear to be a correlation between the presence of HLA-B*35 and high antibody titers, or the presence of CICs. In conclusion, 2 HLA alleles that associate with resistance and 1 that associates with susceptibility to E. granulosus infection have been identified. The joint pain reported by some of the patients might be attributed to CIC deposits.

Pathology of renal diseases in the tropics

Renal diseases unique to the tropics are those that occur in association with infectious diseases including dengue hemorrhagic fever, typhoid fever, shigellosis, leptospirosis, lepromatous leprosy, malaria, opisthorchiasis, and schistosomiasis. These renal complications can be classified on the basis of their clinical and pathologic characteristics into acute transient reversible glomerulonephritis, chronic progressive irreversible glomerulonephritis, amyloidosis, and acute renal failure (ARF) resulting from acute tubular necrosis, acute tubulointerstitial nephritis, and thrombotic microangiopathy. Certain primary glomerular diseases including immunoglobulin (Ig) M nephropathy and focal segmental and global glomerulosclerosis are prevalent in some tropical countries. Renal complications of venomous snakebites also are common in the tropics. This article discusses and summarizes important works in the literature in respect to the clinical syndromes, pathologic features, and pathogenesis of tropical renal diseases both in humans and experimental animal models.

Autoimmunity and malaria: what are they doing together?

A common feature of autoimmunity is the presence of autoantibodies (AAb). Two types of AAb have been described: the 'pathogenic' AAb, associated with autoimmune diseases (AID), and the so-called 'natural' AAb. The latter are present in all normal individuals and have been postulated to play a major role as a first defensive barrier of the organism. Both the 'pathogenic' and the 'natural' AAb can be detected at higher frequencies among individuals exposed to viral, bacterial and parasitic infections. The malaria associated AAb do not seem to result from a generalised polyclonal B-cell activation (PBA), have specificities that may differ according to the degree of clinical immunity and do not seem to be pathogenic. Malaria may offer a protective effect against AID, by diminishing its severity or by either preventing or retarding its expression. AAb could also participate in the immune protection against malaria, and this could happen in several ways: (i) AAb directed to modified Ag expressed on the red blood cell (RBC) membrane during parasitisation and (ii) AAb reactive with crypto- or neo-Ag revealed on both normal and infected RBC membranes, by destroying infected, and also normal, erythrocytes; (iii) anti-idiotype AAb specific of the binding site of anti-merozoite Ab, which would mimic the parasite ligand for the RBC receptor, by competing with parasites and blocking RBC invasion; (iv) AAb cross-reactive with parasite material - such as nuclear or cytoskeleton Ag - having a direct parasiticide activity; (v) the natural AAb network, through its 'anti-bacterial first defense barrier'; and finally (vi) anti-phospholipid (PL) AAb, by neutralizing the pathogenic properties of parasite-derived PL. Finally, in view of currently available knowledge, it is concluded that, since AAb are not always pathogenic, the price for an 'autoimmunity-mediated' protection in malaria would not necessarily be immunopathology and clinical autoimmunity, and a protective role of AAb could be exerted with no danger to the host.

Isolation of antigen from the circulating immune complex in mice infected with Plasmodium berghei

Circulating immune complex (CIC) is known to play a role in pathological glomerular alterations in malaria. However, the nature of the antigens comprising the CIC is still not fully understood. We report here the isolation of the antigen in CIC and its localisation in mice infected with Plasmodium berghei NK65. The antigen was successfully isolated from CIC extracted from the blood of mice infected with P. berghei, by using C1q-coated microplates. The molecular mass of the antigen separated from CIC bound to C1q was found to be 78 kDa. Furthermore, localisation of the antigen was examined by the fluorescent antibody technique and immunoelectron microscopy. The antigen was detected in the parasitised erythrocyte and the mesangial matrix by both methods. These results suggest that the 78 kDa protein might be associated with the glomerular alterations in malaria infection.

Is there a role for autoimmunity in immune protection against malaria?

Much remains to be known about the mechanisms involved in protective immunity against malaria and the way it is acquired. This is probably the reason why, in spite of so much progress, it has not yet been possible to develop an anti-malaria vaccine able to induce parasite specific antibodies (Ab) and/or T-cells. It has been considered in the early 80s that the induction of efficient protection against the blood stage forms of Plasmodium falciparum would not be possible without simultaneously eliciting an autoimmune (AI) response against erythrocytes, even at the price of inducing an AI pathology. Despite the description of the reciprocal relationship, i.e. the protective effect of malaria on the development of AI diseases _ demonstrated since 1970 _ no effort has been made to verify the possible involvement of the AI response in protection against malaria.

Glomerulopathy associated with parasitic infections

Although parasitic infections do not usually present with disturbance in renal function, glomerular lesions can be seen in most of these infections. The glomerular lesions observed in parasitic infections cover the whole range of glomerular lesions known, but most of them are proliferative. Little is known of the exact pathogenic mechanisms. In this review, we try to explain the glomerular lesions associated with parasitic infections in terms of the specific immunologic events observed during these diseases against the background of recent developments in the general knowledge of the pathogenesis of glomerular disease.

Glomerulopathy associated with parasitic infections

Although parasitic infections do not usually present with disturbance in renal function, glomerular lesions can be seen in most of these infections. The glomerular lesions observed in parasitic infections cover the whole range of glomerular lesions known, but most of them are proliferative. Little is known of the exact pathogenic mechanisms. In this review, we try to explain the glomerular lesions associated with parasitic infections in terms of the specific immunologic events observed during these diseases against the background of recent developments in the general knowledge of the pathogenesis of glomerular disease.

Molecular mimicry between host and pathogen: examples from parasites and implication

The studies summarized in this paper suggest that parasites may trigger activation of autoimmune mechanisms. The association between parasites and autoimmunity could by manifested by the development of pathogenic anti-parasitic antibodies and cytotoxic T cells that attack and damage self tissues as a result of molecular mimicry between host and parasites. On the other hand, the homology between self and parasitic antigens may enable parasites to protect themselves from the immune system and to induce a state of immunosuppression. Although classic autoimmune diseases have not been shown to be more common amongst patients with chronic parasitic infections than in the general population, it is clear that autoimmune activity does occur in patients with chronic parasitic infections. It is possible that infection with parasites and other microbial agents may be followed by the activation of the immune system and, in genetically predisposed individuals, by loss of functional tolerance to self, activation of autoreactive cell that leads to progression to an overt autoimmune disease.

Molecular, metabolic and immune evidence suggest that systemic autoimmune disease is antigen-mediated

Patients with systemic lupus erythematosus generate a sustained immune response against self. The tools of modern molecular biology have been applied to cell activities and elements/signals of the immune system, but a structural or regulatory defect has not been found. When deoxyribonucleic acids for autoantibodies were cloned and sequenced, they were like other autoantibody DNA sequences; when genetic materials for autoantibodies were inserted into transgenic mice, cells secreting the antibodies were subject to normal control mechanisms and eliminated. A failure to clear self-reactive antibody producing thymocytes has not been demonstrated in human systemic lupus erythematosus. Molecular analyses of the efferent side of the immune response have been largely normal in systemic lupus erythematosus. The structure of autoantibodies suggests that they have been generated by selection pressures and the presence of endogenous antigens. If the immune system attack on self was secondary, structural changes and metabolic reactions capable of generating antigens should be found in systemic lupus erythematosus cells. Structural changes have been found in deoxyribonucleic acid from phytohaemagglutinin-stimulated systemic lupus erythematosus lymphocytes in the form of S1 nuclease-sensitive deoxyribonucleic acid breaks. Altered cellular macromolecules could result from endogenous metabolic processes, particularly oxygen free radicals and arachidonic acid metabolites. Excess free-radical species, generating positive nitroblue tetrazolium-reacting material and positive chemiluminescence, have been found in most but not all phytohaemagglutinin-stimulated lupus lymphocyte samples. If endogenous metabolic processes act on endogenous deoxyribonucleic acid, endogenous cell DNA breakdown may lead to low molecular weight deoxyribonucleic acids and deoxyribonucleic acid/immune complexes in systemic lupus erythematosus sera that are potentially immunogenic. These combined findings suggest that the exaggerated immune responses of systemic lupus erythematosus may be a normal response to protect the host from a perceived antigenic threat.

Ligand recognition by murine anti-DNA autoantibodies. II. Genetic analysis and pathogenicity

Although anti-DNA autoantibodies are an important hallmark of lupus, the relationships among anti-DNA structure, reactivity, and pathogenicity have not been fully elucidated. To further investigate these relationships, we compare the variable genes and primary structure of eight anti-DNA mAbs previously obtained from an MRL/MpJ-lpr/lpr mouse along with the ability of three representative mAbs to induce nephritis in nonautoimmune mice using established adoptive transfer protocols. One monospecific anti-single-stranded (ss) DNA (11F8) induces severe diffuse proliferative glomerulonephritis in nonautoimmune mice whereas another anti-ssDNA with apparently similar in vitro binding properties (9F11) and an anti-double-stranded DNA (4B2) are essentially benign. These results establish a murine model of anti-DNA-induced glomerular injury resembling the severe nephritis seen in lupus patients and provide direct evidence that anti-ssDNA can be more pathogenic than anti-double-stranded DNA. In vitro binding experiments using both protein-DNA complexes and naive kidney tissue indicate that glomerular localization of 11F8 may occur by recognition of a planted antigen in vivo. Binding to this antigen is DNase sensitive which suggests that DNA or a DNA-containing molecule is being recognized.

Glomerulopathy associated with parasitic infections

Numerous infectious diseases, among them several parasitic infectious, have been shown to be associated with glomerular disease, although the exact pathogenetic mechanisms have not yet been elucidated. In this article, Marie-Louise van Velthuysen reviews the work published on glomerulopathy associated with the most important parasitic infections, ie. malaria, schistosomiasis, leishmaniasis and irypanosomiasis.

Characterization and pathological significance of monoclonal DNA-binding antibodies from mice with experimental malaria infection

Malaria infection is accompanied by the production of a number of autoantibodies, including some that react with DNA. Epidemiological evidence implicates these in the nephritides that arise in human quartan malaria and in experimental malaria infections in mice. Through parallels with the involvement of DNA-reactive antibodies in the autoimmune syndrome systemic lupus erythematosus, a role for DNA-reactive antibodies in forming phlogistic immune deposits in the kidneys is implied. To more fully understand the relationship between antibodies of this specificity made in malaria and systemic lupus erythematosus, we prepared monoclonal DNA-reactive antibodies from BALB/c mice infected with Plasmodium berghei (clone RC) and compared their properties with those of other antibodies previously isolated from lupous MRL/Mp lpr/lpr and (NZB x NZW)F1 mice. Antibodies from malarial mice were all immunoglobulin M class and bound to single-stranded but not double-stranded DNA in an enzyme-linked immunosorbent assay. They also reacted with synthetic polyribonucleotides in the enzyme-linked immunosorbent assay and with parasitized erythrocytes and parasite pigment in kidney sections. None of the antibodies from lupous mice had identical specificities. The potential involvement of the DNA-reactive antibodies in malarial nephritis was demonstrated, by use of immunocytochemical methods, on the basis of their binding to existing immune deposits in kidney sections from malarial mice, a similar property having been previously demonstrated for antibodies from lupous mice. Furthermore, antibodies from malarial mice expressed public idiotypes, notably Id.V-88, which is a member of the Id.16/6 family, commonly found on DNA-reactive antibodies in lupus and other infectious and connective tissue diseases. This study indicates that DNA-reactive antibodies in malaria have immunochemical properties similar but not identical to those of such antibodies in systemic lupus erythematosus and that they have the potential to participate in the formation of immune deposits in nephritic malarial kidneys.

Murine malaria: anti-erythrocytic antibodies recognize N-acetyl neuraminic acid residues

A cell-ELISA was developed using monolayers of glutaraldehyde-fixed normal as well as Plasmodium berghei-infected mouse erythrocytes for quantification and characterization of anti-erythrocytic autoantibodies in murine malaria. Testing normal (NMS) and peak parasitaemic sera (PPS) on erythrocyte monolayers treated with trypsin, sodium meta periodate, neuraminidase or heat, and competitive inhibition of antibodies with soluble sialic acid, revealed that some anti-erythrocytic antibodies (which increase during the parasitaemic phase of infection) recognize N-acetyl neuraminic acid (NANA) residues on host erythrocytes. High levels of antibodies to NANA covalently conjugated to bovine serum albumin (BSA) were detectable in PPS. Such antibodies could be significantly absorbed out by preincubation of PPS with mouse erythrocytes (MRBC). Antibodies in PPS, when affinity-purified on a column of Fetuin-Agarose, were found to be reactive to normal as well as parasitized erythrocyte monolayers. Immunoglobulin isotyping and IgG subgroup typing revealed that most of the anti-erythrocytic autoantibodies in NMS were IgM and IgA, while in PPS there was an appreciable increase in IgG2a and IgG3. Affinity-purified anti-NANA antibodies reacted with DNA when tested in an ELISA. There was a significant positive correlation between anti-erythrocytic antibody and DNA-binding levels in NMS as well as PPS. The DNA-binding antibodies in PPS could be effectively absorbed out by preincubation of sera with fresh MRBC. Affinity determination of anti-erythrocytic antibodies eluted from MRBC revealed binding characteristics in the following order: MRBC > single-stranded DNA > double-stranded DNA.

Cell-mediated pathology during murine malaria-associated nephritis

We have studied the cellular mechanisms involved in the development of nephritis during acute and chronic murine malaria infections induced by Plasmodium vinckei petteri and P. berghei respectively. Albuminuria and uraemia were observed during the early stages of both types of infection, and were associated with glomerular and interstitial hypercellularity. There was a gradual increase in numbers of CD45+ cells from the early stages of both infections onwards. These infiltrates contained CD4+ and CD8+ cells and mononuclear phagocytes. The interstitial and glomerular hypercellularity was due to an influx of inflammatory cells rather than an increase in renal cell division. These findings indicate the importance of cell-mediated immune mechanisms in the development of nephritis during murine malaria and illustrate an example of naturally occurring infection-induced nephritis.

Parasitic infection and autoimmunity

The studies summarized in this paper indicate that parasitic infections can serve as a trigger factor of autoimmune reactivity by several mechanisms. The relationship between parasites and autoimmunity could be manifested by the presence of autoantibodies or T-cells with autoreactivity. In spite of the evidence that has accumulated, the specific association between infection and autoimmunity is still obscure. The reasons for tissue damage in parasitic diseases are controversial. Some believe it is the result of pathogenic autoantibodies or autoreactive T-cells. Others argue against the causative role of autoimmunity in the formation of tissue lesions. The parasite itself could be the cause of tissue destruction, thus releasing high amounts of self antigens which might stimulate the autoreactivity. There is now little doubt that some degree parasite/host cross-reactivity occurs, and definition of cross-reacting antigens and epitopes is now taking place. It seems likely that a combination of events could result in cross-reactivity including: parasites themselves have cross reactive molecules and altered self antigens by adsorbing of parasite material to surrounding host cells. The mechanisms involved in parasites autoimmunity are complex and numerous, requiring a rigorous experimental approach to rationalize each step and determine its clinical importance. The developed methods in immunochemistry, monoclonal antibodies and hybridoma technology, and recombinant DNA research not only facilitate this kind of approach but also allow optimism for a successful outcome.